Children and Nature: Why Time Outdoors Matters for the Immune System and Nerves
For a young immune system, soil, animals and diversity may be more than just dirt. What farm, daycare and green space studies show, where their limits lie and how to stay safe outdoors as a family.
We protect our children from germs, cold and dirt. That comes from love, and much of it is right. But an immune system learns the way a child does: through encounters, not just through protection.
Do you know this moment? Your child comes in from the garden or the playground. Their hands are black, their knees are green, and there is a leaf caught in their hair. And before you can even smile, you think: wash those hands, right now.
Maybe your child has eczema or hay fever. Then the worry is even bigger. Every meadow looks like a risk, every animal like trouble, every sandbox like a pile of germs.
At the same time, you hear about farm children who have fewer allergies. About daycare centers in Finland that covered their yards with forest floor. And you wonder: What is actually true here, and what does it mean for us?
That is exactly what this is about. Your child's immune system, microbiome and nerves. And the question of how much nature can do them good, and where caution makes sense.
Does nature strengthen children's immune systems? Studies suggest that early and varied contact with nature can shape the young immune system toward tolerance. In large studies, children from traditional farms have asthma and allergies less often. In Finnish daycare studies, forest floor and soil changed the children's skin bacteria and immune markers.
Green spaces are associated with better concentration and mental health, and time outdoors can help prevent nearsightedness. Much of this is based on observations and small studies. They show a direction, not a promise.
What to expect in this article
- What farm children have going for their immune systems
- Why the immune system needs old friends
- What forest floor changed in Finnish daycare centers
- How the gut translates the farm effect
- Dogs, cats and allergy risk
- Green spaces for concentration, stress and mental health
- Why time outdoors matters for the eyes
- If your child already has allergies
- Why free, sometimes risky play matters
- Safe outdoors: ticks, sun, animals
- The four KPNI lenses on a child in the forest
- Three levers for your family's everyday life
What farm children have going for their immune systems
Imagine two communities in the USA. Both make their living from farming. Both lead a very similar lifestyle, and both share a similar genetic ancestry.
One difference only becomes visible in the barn. The Amish farm the traditional way. The Hutterites use industrialized methods.
And then something stands out that has occupied researchers for years. Asthma is much rarer among the children of one community than among those of the other. Before we take a closer look there, it is worth looking back.
How it all began with siblings
The trail leads back to 1989. Strachan from the London School of Hygiene and Tropical Medicine analyzed a large British birth cohort. He noticed: The more older children lived in a household, the less often the younger ones had hay fever.
His hypothesis was that early infections brought home by older siblings might protect against allergies. This later gave rise to the so-called hygiene hypothesis. The term itself only emerged after his work.
Key point: In large studies, early and diverse microbial contact goes along with less asthma and fewer allergies. In rural regions of Central Europe, 1 percent of children with barn exposure in their first year of life had asthma, compared with 11 percent of children whose exposure began later.
Riedler and colleagues from Salzburg surveyed the parents of 2,618 children aged 6 to 13 in rural regions of Austria, Germany and Switzerland. In addition, 901 children provided a blood sample.
Children who spent time in barns and drank farm milk before their first birthday had asthma less often than children whose exposure only began between the ages of one and five: 1 versus 11 percent. For hay fever, the figures were 3 versus 13 percent, and for sensitization 12 versus 29 percent.
What this means for you: The timing seems to matter. Allergies were rarest among children who had continuous barn exposure up to the age of five. As a cross-sectional study, this shows associations, not proof.
Riedler J, Braun-Fahrländer C, Eder W et al. Lancet. 2001. DOI: 10.1016/S0140-6736(01)06252-3Raw milk can contain germs such as Campylobacter or EHEC. In children, an EHEC infection can cause severe, sometimes permanent kidney damage. The German Federal Institute for Risk Assessment therefore generally advises against children drinking raw milk that has not been boiled.
So the association from the studies is no reason to give your child untreated milk. Your child can still experience the barn, the animals and the meadows.
Amish and Hutterites: a natural experiment
A team led by Stein, Ober and Sperling from the University of Chicago compared 60 children from both communities in the New England Journal of Medicine. The researchers measured house dust, blood values and the function of immune cells.
Asthma was four times less common and allergic sensitization six times less common among the Amish children. Amish house dust contained a median of 6.8 times as much endotoxin, that is, components of bacterial cell walls. The cells of innate immunity also differed markedly. In a mouse model, dust from Amish homes protected the airways against an allergic reaction, while dust from Hutterite homes did not.
What this means for you: With similar genes, the environment could make the difference. It seems to train innate immunity early on, a bit like a sparring partner who prepares you for the real thing.
Stein MM, Hrusch CL, Gozdz J et al. N Engl J Med. 2016. DOI: 10.1056/NEJMoa1508749Is it a particular germ that protects? Or the amount? A research group in Munich took a closer look.
Ege, von Mutius and colleagues from Munich analyzed two large European studies, PARSIFAL and GABRIELA. They examined mattress and room dust from farm children and from children in a comparison group.
Farm children were exposed to a greater diversity of environmental microbes and had asthma and allergies less often. The more diverse the microbial environment, the lower the risk of asthma, with an odds ratio of 0.62 in PARSIFAL and 0.86 in GABRIELA. An odds ratio below 1 stands for a lower risk.
What this means for you: What seems to matter is less a single germ than diversity. According to the authors, this diversity explains a substantial part of the farm effect.
Ege MJ, Mayer M, Normand AC et al. N Engl J Med. 2011. DOI: 10.1056/NEJMoa1007302How might barn dust influence the airways? One answer comes from the lab, and it comes from mice.
Schuijs, Lambrecht, Hammad and colleagues from Ghent showed in Science: Repeated exposure to small amounts of endotoxin or farm dust protected mice against asthma caused by house dust mites.
A protein called A20 in the cells of the airway lining was decisive. When it was missing, the protection disappeared. In farm children, a gene variant of A20 was linked to the risk of allergy and asthma.
What this means for you: The mucous membrane is like a bouncer at the door who learns not to flag harmless guests as a danger right away. This is well documented in the animal model, but not yet conclusively in humans.
Schuijs MJ, Willart MA, Vergote K et al. Science. 2015. DOI: 10.1126/science.aac6623The data are now so consistent that they have found their way into the German guideline. The S3 guideline on allergy prevention states: There is clear evidence that growing up on a farm is associated with a lower risk of asthma and allergic diseases. Among other things, it links this to the greater microbial diversity in house dust.
It is not about dirt. It is about diversity.
A farm is not a recipe you have to cook up at home. It is a clue to what a young immune system in the city might be missing: contact with many different, mostly harmless microbes, from early on and on a regular basis.
You don't have to move to the countryside for this. A visit to a farm with barns, animals and meadows can be a lovely family ritual, especially for city kids. Perhaps more important than any single visit is the attitude behind it: encounter instead of shielding.
And now you know why researchers look at barns, cows and house dust with such curiosity.
Old friends: why the immune system needs company
Have you ever wondered why allergies seem almost part of the package in so many families today? Hay fever in one child, eczema in another, a nut allergy in the daycare group.
Researchers around the world describe an increase in allergies and other chronic inflammatory diseases, especially in cities. One possible explanation has to do with friendship.
Imagine your child's immune system as a young soccer team. There are strikers who attack. And there are referees who blow the whistle when the game gets too heated. These referees are called regulatory T cells. One of their most important messengers is IL-10, a signal to calm down.
With an allergy, the referee blows the whistle too late. The immune system treats pollen, animal dander or food proteins as if they were attackers.
Rook from University College London describes the principle behind this with a lovely image: the old friends. This refers to microbes and other organisms that humans have lived alongside throughout their entire evolutionary history. The immune system had to tolerate them. In this way, they came to play a role in training the referees.
Some of these old friends have almost disappeared from city life. According to Rook, this makes the microbes that come from the mother, from other people, from animals and from the environment all the more important.
Rook's caution is remarkable. For him, quick relaxation effects in green surroundings do not yet prove a long-term health benefit. His argument is a different one: Nature provides microbial input that the immune system needs in order to regulate itself.
Key point: Tolerance is something the immune system learns, and harmless microbes could be the teachers. In adolescents prone to allergies, researchers found less biodiversity around the home and less bacterial diversity on the skin.
Hanski, Haahtela and colleagues from the University of Helsinki examined a random sample of adolescents from a region of Finland with a varied landscape.
Adolescents with an allergic predisposition lived in surroundings with less biodiversity. On their skin, there were fewer different gammaproteobacteria, a group of bacteria that is also common in soil and on plants. In healthy adolescents, more Acinetobacter, a member of this group, went along with more IL-10 in immune cells.
What this means for you: The landscape outside your front door could reach all the way onto the skin and into the immune cells. A cross-sectional study only shows associations, however, not a cause.
Hanski I, von Hertzen L, Fyhrquist N et al. Proc Natl Acad Sci U S A. 2012. DOI: 10.1073/pnas.1205624109Is dirt healthy for children?
It is not dirt itself but contact with many different, mostly harmless microbes that seems to train the immune system. Hygiene that is meant to protect against infections remains important. It just needs to be targeted rather than blanket.
A group led by Bloomfield and Rook consulted six experts on infections and allergies in a structured consensus process. The group considers the term hygiene hypothesis misleading.
In their view, there is no good evidence that everyday hygiene, as most people understand it, is responsible for the relevant changes. As possible building blocks, they name breastfeeding, more time outdoors, less time indoors, social contact, diet and an appropriate use of antibiotics, among others. Prevention, they say, needs to start early in life.
What this means for you: Targeted hygiene means being consistent where infections are a threat and relaxed everywhere else.
Bloomfield SF, Rook GA, Scott EA et al. Perspect Public Health. 2016. DOI: 10.1177/1757913916650225Hygiene and nature are not opponents.
Washing hands before eating, after using the toilet and after contact with animals can protect against infections. In between, a child is welcome to dig in the sand, look for earthworms and throw leaves. The two belong together.
Maybe you are now thinking of things you can no longer change. A C-section, antibiotics in the first year of life, an apartment without a garden. That is no reason to feel guilty. Many of these decisions were right and necessary.
The early window seems to be especially formative. Even so, the immune system stays in exchange with its environment throughout life. Being outdoors is a building block that is open to your family every day.
And now you know why researchers today prefer to talk about diversity rather than dirt.
Forest floor instead of safety mats: what Finnish daycare centers showed
Think of the yard at your child's daycare. Maybe paving stones, gravel, a sandbox and a rubber mat under the swing. Practical, clean, easy to maintain.
A Finnish research team asked what happens when a yard like that becomes a piece of forest. It is one of the few places where the biodiversity hypothesis was not only observed but tested in an experiment.
Key point: In daycare studies, just a few weeks of contact with diverse soil went along with changes in skin bacteria and immune markers. In the double-blind sandbox study, the children played for 20 minutes twice a day.
Roslund, Sinkkonen and colleagues from the University of Helsinki brought forest floor, sod and planter boxes into the yards of urban daycare centers. For comparison, they examined children from standard urban daycare centers and from nature-oriented daycare centers.
After 28 days, the diversity of gammaproteobacteria in the surroundings and on the children's skin was greater. This went along with a rise in the messenger TGF-β1 in the blood and a higher proportion of regulatory T cells. The ratio of IL-10 to IL-17A, in other words of brake to gas pedal, increased.
What this means for you: A few weeks of contact with living soil could leave traces in the immune system. However, the daycare centers were not randomly assigned, and what was measured were lab values, not illnesses.
Roslund MI, Puhakka R, Grönroos M et al. Sci Adv. 2020. DOI: 10.1126/sciadv.aba2578Two years later, the group tested its idea more rigorously, double-blind and with a placebo. Children aged three to five played in a sandbox for 20 minutes twice a day for 14 days. In one group, the sand was enriched with microbially diverse soil. In the other, it was only colored with peat and looked the same.
Only in the soil group did the skin bacteria shift toward those of the sand, and this was still the case 28 days after the start. Compared with the placebo group, IL-10 and the ratio of IL-10 to IL-17A developed in the direction of immune regulation.
What this means for you: Diverse soil seems to engage the immune system differently than sand alone. With 13 children per group, this remains an early but methodologically sound indication.
Roslund MI, Parajuli A, Hui N et al. Ecotoxicol Environ Saf. 2022. DOI: 10.1016/j.ecoenv.2022.113900A difference also remained visible over a longer period. In a two-year analysis by the same research group, the skin of children from the redesigned daycare centers showed a greater variety of proteobacteria after one year. Potentially disease-causing bacteria were less common than in children from standard daycare centers. As a next step, the authors call for studies of immune responses and illnesses.
What speaks for it: Here, the biodiversity hypothesis was not just observed but tested in an experiment, once even double-blind and with a placebo.
What speaks against it: The groups were small, the observation period was short, and what was measured were bacteria and messengers, not allergies.
My conclusion: a promising indication, but not yet proof of fewer illnesses.
A lab value is a clue, not a diagnosis.
A higher IL-10 level does not mean that a child will not develop an allergy. It shows a direction in which the immune system could be moving. For a healthy child, living soil is therefore more of an opportunity than a risk.
Ask at your child's daycare or school whether the yard has flower beds, grass, leaves or a patch of natural ground. With a sandbox, hygiene still counts: Covering it overnight keeps cats away, which might otherwise use it as a toilet. And don't mix garden soil into the sand on your own. The studies used tested material.
And now you know why a patch of forest floor in the daycare yard could be more than decoration.
The gut matures too: microbiome, butyrate and the farm effect
In the first year of life, something astonishing happens in your child's belly. From just a few bacterial species, a whole ecosystem gradually emerges.
Imagine a young garden. Which plants take root first shapes what it looks like years later. The gut microbiome might be similar.
Key point: A gut microbiome that matures early could explain part of the farm effect. In the European PASTURE study, it was around 19 percent.
In the European PASTURE study, Depner, Ege, von Mutius and colleagues followed children from rural regions from birth. They determined how far the gut microbiome had matured between the second and twelfth month of life.
A more mature microbiome at twelve months was associated with farm exposure and with a lower risk of asthma at school age, odds ratio 0.72. This maturation explained around 19 percent of the farm effect. Children with asthma had less butyrate in their stool and fewer bacteria that produce butyrate.
What this means for you: The path from the barn to the lungs could lead through the gut. Researchers speak of a gut-lung axis.
Depner M, Taft DH, Kirjavainen PV et al. Nat Med. 2020. DOI: 10.1038/s41591-020-1095-xButyrate is a short-chain fatty acid. Gut bacteria produce it when they ferment dietary fiber. You can think of it as a text message that the gut sends to the immune system. Its content might read: All quiet here, no reason to get worked up.
A Swiss research group led by Roduit found something similar in 301 one-year-old children. Children with the highest butyrate and propionate levels in their stool were later sensitized less often and had asthma less often between the ages of three and six. In mice, these fatty acids dampened allergic inflammation of the airways. This is an animal finding that still needs to be tested in humans.
Can you buy diversity in capsules?
The obvious question is: Why not just take a probiotic? The German S3 guideline on allergy prevention sees insufficient evidence that prebiotics, probiotics or vitamin D supplements can prevent allergies. For the first time, it explicitly advises against giving them for this purpose.
Diversity doesn't come in a can.
A probiotic contains a manageable number of selected strains. A forest floor, a dog or a vegetable patch brings along a whole landscape of microbes, and it does so via the skin, airways and gut at the same time.
For your child's gut, the basics matter more than supplements. A varied, age-appropriate diet with vegetables and fiber. Time with people, animals and nature. And antibiotics when they are medically necessary, decided together with your pediatrician. You can find more on this in my articles on fermented foods and on the gut after antibiotics.
And now you know why allergy researchers now also take a look inside the diaper.
Dogs, cats, children's rooms: what pets can mean
“We would love to have a dog. But our child already has eczema.” Maybe you know this sentence from your own family.
Many parents have heard: If there is a risk of allergies, better no pet. The data now paint a more nuanced picture.
Key point: In large studies, a dog in the first year of life goes along with slightly less asthma. In Sweden, the odds ratio among more than one million children was 0.87.
Ownby and colleagues followed children in a suburban area of Detroit from birth to school age.
At six to seven years of age, 33.6 percent of the children without a dog or cat in their first year of life were sensitized in a skin prick test, compared with 34.3 percent of those with one pet. Among children with two or more dogs or cats, it was 15.4 percent.
What this means for you: A single pet made no difference here, but several did. The children were born in the late 1980s, and the study is comparatively small.
Ownby DR, Johnson CC, Peterson EL. JAMA. 2002. DOI: 10.1001/jama.288.8.963Fall, Almqvist and colleagues analyzed registry data on all 1,011,051 children born in Sweden between 2001 and 2010.
A dog in the first year of life was associated with less asthma at the age of six, odds ratio 0.87. For contact with farm animals, the odds ratio was 0.48. In children under three, a dog was not associated with a lower risk.
What this means for you: The association is measurable, but moderate. A dog is a possible building block, not a protective shield.
Fall T, Lundholm C, Örtqvist AK et al. JAMA Pediatr. 2015. DOI: 10.1001/jamapediatrics.2015.3219A group in Gothenburg led by Hesselmar even found a dose relationship. The more dogs and cats lived in the household during the first year of life, the less often the children had allergies at the age of seven to nine. In the cross-sectional group, the proportion fell from 49 percent in children without pets to zero in children with five or more pets. The authors speak of a mini farm effect.
And it is not only about allergies. In a Finnish birth cohort of 397 children, babies with a dog in the home were healthier overall during their first year of life. They had respiratory symptoms and middle ear infections less often and needed fewer courses of antibiotics.
Still, it is not quite that simple. In the Danish National Birth Cohort with up to 84,478 children, the associations were weak overall. Contact with dogs went along with slightly less eczema and asthma, and a bird in the household during pregnancy with slightly more asthma. Whether an association appeared depended on the type of animal, the timing and family history.
The German S3 guideline on allergy prevention by Kopp and colleagues is based on 286 evaluated studies. On pets, it makes a tiered recommendation.
In families without a recognizably increased allergy risk, keeping a cat or dog should not be restricted as a matter of principle. Families with an increased allergy risk or with a child who already has eczema should not get a new cat. Getting a dog, on the other hand, is not discouraged.
What this means for you: Deciding on a pet is a family decision, not an allergy treatment. If your child is at increased risk, a conversation with your pediatrician beforehand is worthwhile.
Kopp MV, Muche-Borowski C, Abou-Dakn M et al. Allergol Select. 2022. DOI: 10.5414/ALX02303EA dog is not a medicine. It is a family member with fur, paws and microbes.
If a dog fits your life, it could help shape your child's immune system along the way. Bought purely as allergy prevention, it would carry an expectation it does not have to fulfill.
Relaxed and safe with animals
- Wash hands after playing with animals and before eating. That is the most important hygiene step.
- Have pets cared for, vaccinated and dewormed by a vet on a regular basis.
- Don't let infants be licked on the face, and keep food bowls out of reach.
- Reptiles such as turtles, lizards and snakes often carry salmonella. Close contact is therefore not suitable for toddlers.
- Wash out scratch and bite wounds thoroughly, and have them checked by a doctor if there is redness, swelling or fever.
And now you know why a dog is not a prescription against allergies, but not automatically a risk either.
Green for the nerves: concentration, stress and mental health
You may know this after a rainy day indoors. Your child jumps over the sofa, argues with their siblings, nothing is right. Then an hour in the park, and on the way home they are quiet and tired, in the good way.
There is more to this than just tiring them out. In children, as in adults, the stress hormone cortisol follows a daily rhythm. In the morning, it is high and makes you alert, and over the course of the day it falls, like the tide going out after high water. If this rhythm gets thrown off, a child can be wound up in the evening and exhausted in the morning.
Dettweiler and colleagues followed 48 children around eleven years old in Germany for one school year. Of these, 37 spent one full school day per week in the forest, while 11 learned only in the classroom.
On forest days, salivary cortisol fell steadily over the school day, as it does in a child's healthy daily rhythm. In the comparison group, this decline was missing. Statistically, the greater physical activity did not explain the difference.
What this means for you: Learning outdoors could take some pressure off children's stress rhythm. The groups were small and not randomly assigned.
Dettweiler U, Becker C, Auestad BH, Simon P, Kirsch P. Int J Environ Res Public Health. 2017. DOI: 10.3390/ijerph14050475Key point: Green space in childhood is linked to better mental health. In Denmark, people with the least green space in childhood had an up to 55 percent higher risk of later mental disorders.
Engemann and colleagues from Aarhus University used satellite data to calculate, for around one million people in Denmark, how green their residential surroundings were from birth to age ten.
Those who grew up with the least green space around them later had an up to 55 percent higher risk of various mental disorders than those with the most green space. The association remained even after accounting for urbanization, socioeconomic status and parental mental illness.
What this means for you: It was not the single outing but green space throughout childhood that seemed to count. Cause and effect cannot be proven with data like these, however.
Engemann K, Pedersen CB, Arge L et al. Proc Natl Acad Sci U S A. 2019. DOI: 10.1073/pnas.1807504116Another Danish registry study with 814,689 people looked at ADHD. Children from the least green residential areas were diagnosed with ADHD more often. After social factors were taken into account, the association weakened considerably, with the incidence rate ratio falling from 1.55 to 1.20, but it persisted.
In Barcelona, a team led by Dadvand followed 2,593 primary school children aged seven to ten over one year. More green space around the school went along with greater progress in working memory and a greater decrease in inattentiveness. Part of this could be explained by lower air pollution, 20 to 65 percent depending on the analysis.
Taylor and Kuo from the University of Illinois had 17 children aged 7 to 12 with an ADHD diagnosis go for 20-minute walks on three separate occasions: through a park, through downtown and through a residential neighborhood. The order was random.
After the walk in the park, the children concentrated better on a test in which they repeat sequences of numbers backward than after the other two walks.
What this means for you: Twenty minutes of green could improve attention in the short term. This is a complementary building block, not a substitute for ADHD treatment.
Taylor AF, Kuo FE. J Atten Disord. 2009. DOI: 10.1177/1087054708323000How robust is all this? A Danish review by Mygind and colleagues analyzed 84 publications on immersive nature experiences in children and adolescents. It found conditional support for self-esteem, self-efficacy, resilience and academic performance. For mood, the results were less clear, and many studies had a high risk of bias.
In the anthroposophic view of child development following Rudolf Steiner, the so-called lower senses play a special role: the sense of touch, the sense of life, the sense of self-movement and the sense of balance. There, they are seen as the foundation on which thinking and feeling later unfold.
Uneven forest floor, wind, cold and warmth engage precisely these senses. This is a pedagogical tradition without a strong research base. But it fits well with what research on movement, balance and attention suggests.
Fidgeting is often not misbehavior, but a need.
Behind restlessness, there can be a longing for movement, open space and stimuli that the body can process. Indoors, this need runs into walls. Outdoors, it finds a place.
Plan green routes: the detour through the park on the way to school, homework in the garden or on the balcony, an afternoon in the forest on the weekend. Daylight plays a part too, because it is the most important timekeeper of the internal clock. You can find more on this in my article on morning light and the internal clock.
And now you know why an afternoon in the park can be more than a pastime for your child.
Light for the eyes: why time outdoors can help prevent nearsightedness
Books, tablets, homework, building blocks: Children's eyes spend a lot of time looking at things up close these days. In many families, the first pair of glasses lands on the table at some point.
Nearsightedness (myopia) usually develops because the eyeball grows too long during childhood. The retina is not a passive screen in this process. It is an outpost of the brain, and it responds to light.
Key point: More time outdoors can make new nearsightedness less common. In a study with 1,903 first graders, 30.4 instead of 39.5 percent of the initially non-nearsighted children became nearsighted.
He, Morgan and colleagues randomly divided twelve primary schools in Guangzhou into two groups. In six schools, first graders had an additional 40-minute class outdoors every school day, and the parents were encouraged to increase outdoor time.
After three years, 30.4 percent of the initially non-nearsighted children in the outdoor group had become nearsighted, compared with 39.5 percent in the comparison group.
What this means for you: Even one additional outdoor class a day was associated with less new nearsightedness. The study took place in China, where nearsightedness is very common.
He M, Xiang F, Zeng Y et al. JAMA. 2015. DOI: 10.1001/jama.2015.10803In Taiwan, Wu and colleagues encouraged first graders in a school program to spend up to eleven hours a week outdoors and measured light intensity with light meters.
After one year, nearsightedness increased less in the program group, and the risk of rapid progression was 54 percent lower. This applied to children with and without existing nearsightedness.
What this means for you: According to the authors, bright sunlight was not necessary for this. Lower light intensities over a longer period, for example under trees, could also work.
Wu PC, Chen CT, Lin KK et al. Ophthalmology. 2018. DOI: 10.1016/j.ophtha.2017.12.011Light for the eyes doesn't require a sunburn.
For the eyes, what seems to count is the amount of light over time, not the blazing midday sun. Shade under trees is usually still many times brighter than a child's bedroom. That way, eyes and skin can be protected at the same time.
Time outdoors does not replace an eye exam. If your child squints, moves close to books or complains of headaches, they should see an eye doctor.
And now you know why the playground is also a place for the eyes.
If your child already has allergies: outdoors, yes, but wisely
When a family withdraws indoors
I know this pattern very well, often from conversations with parents who bring their worries about a child to a consultation. The child has eczema and struggles with hay fever in spring. Over the years, the family has withdrawn indoors, step by step.
What strikes me in conversations like these: Medically, the child is usually well looked after, with dermatological care and a plan for pollen season. What is missing is time outdoors that nobody organizes. No class, no appointment, just being outside.
Together, we then think about how more free time outdoors could work without ignoring the allergy, in coordination with the child's pediatrician. The existing treatment continues unchanged. Little by little, the parents build in unscheduled afternoons outdoors, adapted to pollen counts and the state of the skin.
When families take this step, I often hear similar things afterward. The afternoons become calmer, and the child falls asleep more easily at night. And above all, the parents describe one thing: less fear of the outdoors.
One distinction is important, and it gets lost in many guides. The studies on farms, animals and biodiversity mainly concern prevention, that is, the time before an allergy develops. Whether contact with nature changes an existing allergy has hardly been studied.
On top of that: Green does not equal diversity. An analysis that seems surprising at first glance shows this.
Lambert and colleagues from Melbourne pooled eleven studies on greenness around the home and allergic respiratory diseases in children.
The results were contradictory. Pooled, the odds ratio was 1.01 for asthma and 0.99 for hay fever, meaning no clear association, with large differences between the studies.
What this means for you: A green neighborhood is not automatically a diverse one. Lawns, ornamental plants and pollen could affect an immune system differently than a species-rich forest with living soil.
Lambert KA, Bowatte G, Tham R et al. Environ Res. 2017. DOI: 10.1016/j.envres.2017.08.002Outdoors with allergies or eczema
- Always have the allergy plan with you: medication and, if prescribed, the emergency kit.
- During heavy pollen periods, shift time outdoors to hours with lower pollen counts or go out after a rain shower.
- After playing outside during pollen season, change clothes and wash the hair, especially before bed.
- With eczema, gently cleanse and moisturize the skin after sand and mud, and protect open, weeping areas from soil.
- With asthma, discuss with your pediatrician how to handle cold, exertion and pollen.
An allergy is not house arrest.
The goal is not to avoid every encounter with nature. It is about shaping those encounters so that your child tolerates them well. With eczema, it is also worth looking at the connection between the gut and the skin, which I describe in my article on the gut-skin axis.
And now you know why prevention and treatment are two different questions.
Free play, sometimes risky: why unscheduled time matters
Do you remember your own childhood outdoors? Treehouses, puddles and afternoons without a plan, when you only came home for dinner?
Many children experience this less often today. Their day is tightly scheduled: daycare, class, appointment. Being outdoors often means standing on a standardized playground under supervision.
Key point: Free play with a certain amount of risk goes along with more physical activity and better social health. A review of 21 studies shows this.
Brussoni and colleagues from the University of British Columbia analyzed 21 papers on risky outdoor play, meaning play with more freedom and a certain amount of risk.
Overall, they found positive effects on various health indicators, most often on physical activity, but also on social health and behavior.
What this means for you: A child who is allowed to figure out for themselves how high to climb trains more than muscles. They learn to assess risks. The authors would like to see more high-quality studies, but they speak out in favor of more such opportunities.
Brussoni M, Gibbons R, Gray C et al. Int J Environ Res Public Health. 2015. DOI: 10.3390/ijerph120606423Outdoors, a child's immune system is not the only thing that learns. The child gets to know themselves: how far they can jump, what cold feels like, when they need help. That is a freedom no toy and no supplement can replace.
Plan the time, but not what happens in it. Offer places where your child can climb, build, play in the mud and sometimes put up with boredom, too. Stay within earshot and let them explore their own limits, adapted to their age and the terrain. If your child goes barefoot while doing so, you will find more about children's feet in my article on walking barefoot.
And now you know why an afternoon without a program is not a wasted afternoon.
Safe outdoors: ticks, sun, animals and what should be checked
Maybe you are thinking: That all sounds nice, but what about ticks? Sunburn? The neighbors' dog?
These questions are legitimate. Contact with nature is most valuable when you know the real risks and approach the rest with ease.
A review by Stanek and colleagues in the Lancet describes erythema migrans, a spreading red rash, as the most common sign of Lyme disease, which is transmitted by ticks. The pathogen can spread to the skin, nervous system, joints or heart. If the disease is recognized and treated, most people recover well. The most important prevention is protection against tick bites, because there is no Lyme disease vaccine for humans.
Ticks
Long clothing in meadows and undergrowth. Check for ticks in the evening, especially on the head, neck, armpits, backs of the knees and groin. Remove ticks early and in one piece. In risk areas for tick-borne encephalitis (TBE), Germany's Standing Committee on Vaccination (STIKO) recommends vaccination, so ask your pediatrician about it.
Sun
Shade, clothing and a hat are the simplest shields. In summer, it is better to spend the midday hours in the shade. Babies should be kept out of direct sunlight. More on this in my article How much sun does the body need.
Animals
Wash hands after contact with animals and before eating. Only pet unfamiliar dogs after asking the owner. Reptiles are not for toddlers because of salmonella.
Farm milk
Always boil raw milk for children. The German Federal Institute for Risk Assessment warns of germs such as Campylobacter and EHEC.
Soil and wounds
Rinse scrapes thoroughly with water. Check the vaccination record to see whether tetanus protection is up to date.
Berries and mushrooms
Teach young children early not to put anything unfamiliar in their mouths. Save the number of your poison control center in your phone.
A word on vaccination, since it often comes up in this context. The S3 guideline on allergy prevention finds no evidence that vaccinations increase the risk of allergies, rather indications pointing the other way. It recommends vaccinating all children according to current recommendations, including children at risk of allergies. Being outdoors complements vaccine protection. It does not replace it.
Children with a congenital or acquired immunodeficiency, on medication that suppresses the immune system, with a history of a severe allergic reaction, or with severe asthma or extensive, open eczema need an individual plan. Talk to your pediatrician before you significantly expand contact with animals, barn visits or gardening projects.
Seek medical help immediately if your child has shortness of breath or swelling after an insect sting, deep bite wounds, or fever, a spreading red rash or facial paralysis after a tick bite.
And now you know why good preparation does not make contact with nature smaller, but freer.
The four KPNI lenses on a child in the forest
In clinical psychoneuroimmunology (KPNI), we do not look at just one organ. We ask how the nervous system, immune system, metabolism and hormonal system interact. In a child playing in the forest, all four interlock.
Learning tolerance
Diverse microbes from soil, animals and plants could promote regulatory T cells and messengers such as IL-10 and TGF-β1, the brakes of the immune system. In the animal model, the airway lining learns via the protein A20 to react more calmly to harmless stimuli.
The gut as translator
A gut microbiome that matures early produces more butyrate, a short-chain fatty acid made from dietary fiber. In cohort studies, high butyrate levels went along with less asthma and sensitization. Sunlight on the skin also provides the impulse for the body's own vitamin D production.
Rhythm instead of constant stress
Cortisol follows a daily rhythm, high in the morning and falling over the day. In children with a forest school day, it fell steadily over the school day. Daylight also sets the internal clock and with it the timing of the sleep hormone melatonin.
Senses, attention, eyes
Uneven ground can challenge balance and body awareness. In studies, green space went along with better attention and fewer mental disorders. The retina, an outpost of the brain, seems to need daylight to keep the eye's growth in length in balance.
And now you know why contact with nature is not a topic for a single organ, but for the whole child.
How solid the evidence is
Not everything in this article is equally well supported. To help you put the statements in context, here is an overview of the levels.
From well documented to experience
In two cluster-randomized studies, more time outdoors at school went along with less nearsightedness.
Growing up on a traditional farm is linked to less asthma and fewer allergies, and the S3 guideline speaks of clear evidence. Green space in childhood is linked to better mental health. Cause and effect have not been proven here.
In small studies, biodiversity in daycare centers changed skin bacteria and immune markers. Butyrate and microbiome maturation could help carry the farm effect. So far, the A20 mechanism has mainly been shown in the animal model.
The anthroposophic theory of the senses is a pedagogical tradition. In my practice, I observe that families with more free time outdoors seem more relaxed. That is experience, not a study.
Three levers for your family's everyday life
You don't have to change everything at once. Three directions are enough to start with.
Outside every day, without a program
Plan time outdoors like a fixed appointment, but don't fill it. In the studies, even manageable amounts of time went along with measurable changes: an extra 40 minutes per school day for nearsightedness, twice 20 minutes in the sandbox for immune markers. The direction is: a little every day rather than one big outing a month, and in the rain, too.
Bring diversity into play
Real soil instead of just rubber mats, a vegetable bed on the balcony, leaves, forest, a stream and, if it suits your family, animals. Add targeted hygiene instead of constant alarm: washing hands before eating, after using the toilet and after contact with animals. In between, things are allowed to get dirty.
Weave green into everyday life
The way to school through the park, the daycare with a nature garden, the weekend in the forest. Ask at your child's daycare or school whether the yard could use more nature. The Finnish studies show that this does not take a farm, but soil, plants and time.
In the end, contact with nature is not a method. It is an invitation to your child to get to know the world with all their senses, and to you to trust a little more.
And now you know why dirty hands are sometimes the best sign of a good day.
Frequently asked questions about nature, children and the immune system
Does nature strengthen children's immune systems?
Studies suggest that early and varied contact with nature can shape a child's immune system toward tolerance. In large observational studies, children from traditional farms have asthma and allergies less often, and the German S3 guideline on allergy prevention speaks of clear evidence for an association here.
In Finnish daycare studies, forest floor and microbially diverse soil changed the children's skin bacteria and some immune markers within a few weeks. Whether this leads to fewer illnesses in the long term has not yet been shown. That is why learning is a more fitting word than strengthening: The immune system learns to tell harmless stimuli apart from real dangers.
Is dirt healthy for children?
It is not dirt itself that seems to be decisive, but contact with many different, mostly harmless microbes from soil, plants, animals and other people. An expert group led by Bloomfield and Rook therefore considers the term hygiene hypothesis misleading and recommends targeted hygiene.
That means: washing hands before eating, after using the toilet and after contact with animals, keeping wounds clean, boiling raw milk. In between, your child can dig in the sand, rummage through the leaves and get dirty.
What is the old friends hypothesis?
The old friends hypothesis is closely associated with the London researcher Rook. It holds that over the course of human history, our immune system developed together with microbes and organisms that it had to tolerate.
These old friends came to play a role in calibrating the immune brakes, for example via regulatory T cells. If they are missing from modern city life, immune regulation might not work as well. The hypothesis is well founded, but not proven in every respect.
Does farm life protect against allergies?
In many studies, children who grow up on traditional farms with livestock from an early age have asthma, hay fever and sensitizations less often. Among Amish children, whose families farm traditionally, asthma was four times less common and sensitization six times less common than among Hutterite children from industrialized farming.
The association seems strongest when contact begins in the first year of life and continues for a long time. Raw milk from the farm should not be part of it, however: The German Federal Institute for Risk Assessment generally advises against children drinking unboiled raw milk, because it can contain dangerous germs.
Should we get a dog to prevent allergies?
A dog is not a medicine, but it is not an allergy risk that you have to avoid on principle, either. In a Swedish registry study of more than one million children, a dog in the first year of life was associated with slightly less asthma at age six.
The German S3 guideline recommends not generally restricting pet ownership in families without an increased allergy risk. With an increased risk or existing eczema, it advises against getting a new cat, but not against getting a dog. Above all, a pet should fit your family life.
My child already has hay fever or eczema. Does time outdoors still make sense?
In the vast majority of cases, yes, but with a plan. The studies on farms and biodiversity mainly concern prevention, and whether contact with nature changes an existing allergy has hardly been studied. Time outdoors can still be valuable for movement, stress relief and enjoyment of life.
During pollen season, it is worth moving time outdoors to hours with lower pollen counts or to after a rain shower, then changing clothes and washing the hair. With eczema, the skin should be gently cleansed and moisturized after sand and mud. Medication and, if prescribed, the emergency kit always belong in the bag.
How much time outdoors is good for children?
There is no fixed number. The studies do, however, point to manageable amounts: In China, an additional 40-minute outdoor class per school day was associated with less new nearsightedness, and in Taiwan, children were encouraged to spend up to eleven hours a week outdoors.
In the Finnish sandbox study, the children played for 20 minutes twice a day, and even that went along with measurable changes on the skin and in the blood. In the Danish green space study, what counted most was green space throughout childhood. So the direction is: daily rather than rarely, and in almost any weather.
Can playing outdoors protect against nearsightedness?
Randomized school studies support this. In Guangzhou, 30.4 percent of the initially non-nearsighted children with an additional outdoor class per school day became nearsighted within three years, compared with 39.5 percent in the comparison group. In Taiwan, children in an outdoor program had a 54 percent lower risk of rapid progression of nearsightedness.
According to the authors, bright sunlight was not necessary for this, and lower light intensities, for example in the shade of trees, could also work. Time outdoors does not replace a checkup with an eye doctor if your child has trouble seeing.
Does nature make children calmer and more focused?
Studies suggest that green space can support concentration and stress regulation. In Barcelona, primary school children with more green space around their school made greater progress in working memory within one year. Children with ADHD were able to concentrate better after a 20-minute walk in a park than after a walk through the city.
In children with one forest school day per week, the stress hormone cortisol fell steadily over the school day, but not in the comparison group. These are complementary findings, not a substitute for diagnosis or treatment.
Are probiotics a substitute for contact with nature?
As things stand today, probably not. The German S3 guideline on allergy prevention sees insufficient evidence that prebiotics, probiotics or vitamin D supplements prevent allergies, and for the first time explicitly advises against giving them for this purpose.
A probiotic contains a few selected strains. Soil, plants, animals and people bring a much greater diversity, and they do so via the skin, airways and gut. Whether a supplement makes sense for other reasons is a question to discuss with a doctor.
How can I protect my child from ticks and the sun outdoors?
With ticks, what matters most is avoiding bites and removing ticks early. Long clothing in meadows and undergrowth and checking for ticks in the evening, especially on the head, neck, armpits, backs of the knees and groin, are the most important habits. A spreading red rash (erythema migrans) or a fever after a tick bite should be seen by a doctor. In risk areas for tick-borne encephalitis (TBE), Germany's Standing Committee on Vaccination (STIKO) recommends vaccination, so ask your pediatrician about it.
When it comes to the sun, shade, clothing and a hat are the simplest shields, especially at midday in summer. Babies should be kept out of direct sunlight.
What can city families without a garden do?
More than many people think. A balcony planter with soil, a community garden, the park on the way to school or the forest on the weekend bring diversity into everyday life. In the Finnish daycare studies, forest floor, sod and planter boxes in the yard were enough to measurably change the children's skin bacteria.
Ask at your child's daycare or school whether the yard could use more nature. And if a pet fits your life, it brings a piece of nature into your home, too.
When should I talk to a doctor before increasing contact with nature?
Whenever your child has a congenital or acquired immunodeficiency, takes medication that suppresses the immune system, has had a severe allergic reaction before, or has severe asthma or extensive, open eczema. In that case, an individual plan is needed before you significantly expand contact with animals, barn visits or gardening projects.
Your child needs immediate medical help in case of shortness of breath or swelling after an insect sting, deep bite wounds, or fever, a spreading red rash or facial paralysis after a tick bite.
More from the Guide to Natural Forces
Further topics in this cluster
- Using natural forces in everyday life: the overview
- Forest bathing: what happens in the body
- Forest bathing for stress and burnout
- Walking barefoot for feet and posture
- Grounding and earthing: what there is to it
- Fresh air and oxygen
- How much sun does the body need
- Vitamin D deficiency in winter
- Sun, serotonin and mood
- Winter depression and lack of light
- Morning light and the internal clock
- Natural rhythms and the biological clock
- Red light and infrared
- Cold, the immune system and hormesis
- Ice bathing for beginners
- Cold showers in the morning
- Contrast showers and Kneipp in everyday life
- Sauna and the heart: how often
- Warmth and heat hormesis
- Breathing techniques and the vagus nerve
- 4-7-8 breathing for falling asleep
- Mouth taping and nasal breathing
- The full moon and sleep
- Weather sensitivity, air pressure and joints
If the immune system and microbiome keep you thinking
Gut and skin: acne, rosacea, eczema
How the gut and skin may be connected via the immune system
Fermented foods
What sauerkraut, kefir and kimchi can do for the microbiome
The gut after antibiotics
What can support rebuilding the microbiome
Vitamin D and the immune system
What is documented and where the evidence gets thin
Understanding autoimmune diseases
Why the immune system can turn against the body itself
Exercise and the gut
How physical activity can shape the microbiome
Sources
All information was checked against the original abstracts in PubMed, and the figures are taken from the abstracts. Most studies on the farm effect, pets and green spaces are observational studies and show associations, not causes. The Finnish daycare studies are small and short, and they measure bacteria and immune markers, not illnesses. The studies by Stein, Schuijs and Roduit include mouse models. These findings are labeled as animal studies in the text and have not yet been conclusively confirmed in humans. The recommendation on raw milk comes from the German Federal Institute for Risk Assessment.
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