Mold: The Black Hole of Conventional Medicine?

Mycotoxins, the chemical “weapons” of mold, can in experiments be stored in fatty tissue, in organs, and in the nervous system, where they may act neurotoxically, immunotoxically, hepatotoxically, nephrotoxically, as endocrine disruptors, and in some cases as carcinogens. Several hundred mycotoxins have been described, depending on how you count and which source you use.

And: mold does not have to be visible. It can sit inside walls behind wallpaper, in mattresses, in air-conditioning systems, in basements, and in water-damaged building materials. What matters, therefore, is not only the visible patch, but also what you cannot see.

Several mycotoxins may act neurotoxically in lab models. Ochratoxin A (OTA) can cross the blood-brain barrier in lab models and induce neuronal apoptosis there, and it has been linked to Alzheimer-like pathomechanisms. 🔬 In vitro T-2 toxin produced oxidative stress, mitochondrial damage, and neuroinflammation in animal models, measurable in the behavior of the animals, who suddenly become disoriented, more anxious, and cognitively slower. 🐭 In vivo Deoxynivalenol (DON) impaired learning and memory in animal models and triggered aversive emotions via specific brain circuits. Whether this transfers to humans is an open question. 🐭 In vivo

What this can mean in everyday life: imagine you are trying to finish a thought, and mid-sentence it is gone. You know that you were just thinking about something, but what was it? You enter your PIN and three seconds later cannot remember whether you typed it correctly. You read the same paragraph three times and it makes no sense. Many people call this “brain fog,” and from the outside it can sound like a lack of focus or laziness. For those affected, it is real fog.

On top of that comes the over-stimulation. Sounds that used to be normal now feel unbearably loud. A supermarket becomes torture. A conversation in a noisy group is, after twenty minutes, exhausting like a marathon. These are not psychological sensitivities, they could be signs of a nervous system that is permanently in alarm mode. 🏥 Clinical

In the KPNI framework: the immune system is irritated by mycotoxins, releases pro-inflammatory cytokines, those messengers cross the blood-brain barrier, activate microglia (the immune cells of the brain), and the brain enters a “sickness behavior” mode: thinking more slowly, withdrawing socially, low mood, low energy. This is a protective reaction of the body, not a character flaw, not a weakness.

Where these people often end up: in psychiatry (diagnosis: depression, anxiety disorder, adjustment disorder), with the neurologist (MRI unremarkable, nerve conduction normal, work-up for MS or dementia, all without clear findings). The MRIs are unremarkable. Nerve conduction velocity fits. The blood tests show nothing spectacular. And still the daily life feels as if the nervous system were permanently in emergency mode.

Framing the evidence: 👤 Human For human studies on brain fog and cognitive impairment after mold exposure, there is limited, mostly uncontrolled observational data without control groups. RCTs do not exist, they are not ethically feasible. The German AWMF guideline classifies neurotoxic effects from indoor mold as “insufficiently documented.” The mechanisms are biologically highly plausible, the causal human proof is still missing. That does not mean the suffering is not real.

Mycotoxins show a bidirectional immune effect. Depending on dose and duration, they may push the immune system in two opposite directions, which explains the confusion in diagnostics. At low doses, many mycotoxins activate inflammatory pathways (NF-κB), the immune system “fires.” At high doses or with long exposure, they suppress it, the immune system exhausts itself. 🔬 In vitro🐭 In vivo

The clinical picture: those affected by a suppressed immune system pick up small infections constantly, do not properly shake off colds, feel “permanently a little ill.” Those stuck in over-arousal mode react to everything. New allergies appear, intolerances accumulate, skin reactions come and go. Sometimes both phases alternate, which makes diagnosis almost impossible.

Framing the evidence: 👤 Human For autoimmune diseases as a direct consequence of indoor mold exposure, there are no controlled human studies. For the EBV connection, there is experimental mechanistic proof in a cell model. The German AWMF guideline classifies autoimmune diseases through mold as “insufficiently documented.” The clinical pattern remains striking, however, and the silence in the research does not mean the opposite has been proven.

Mitochondria are the energy factories of your cells. They convert glucose and oxygen into ATP, the universal energy currency of the body. Every muscle movement, every thought, every heartbeat, every breath needs ATP. When mitochondria function poorly, the whole system runs short on energy, not in one place, but everywhere at once.

Practically all studied mycotoxins damage mitochondria via the same convergent mechanism: ROS overproduction, breakdown of mitochondrial membrane potential, cytochrome C release, cell death. 🔬 In vitro Ochratoxin A, T-2 toxin, DON, and zearalenone all show this pathway in cell cultures. OTA specifically damages kidney cells via ferroptosis (Zhou et al. 2025). T-2 toxin attacks the mitochondria of nerve cells via the NRF2/PGC-1α pathway (Pang et al. 2022).

Imagine mitochondria like batteries. Under normal stress they can recharge. But if mycotoxins constantly generate ROS (free radicals), the battery is permanently in discharge mode. The body tries to neutralize the free radicals with antioxidants, especially glutathione, the strongest endogenous protective molecule. And then this happens: the glutathione store empties faster than it can be refilled. 🔬 In vitro

This explains an observation I make very frequently in clinical work. 🏥 Clinical When I give people with possible mold exposure glutathione infusions, which should actually be very supportive, some react paradoxically: briefly better, then worse, or even an immediate adverse reaction. One possible explanation: the mobilized glutathione could accelerate mycotoxin clearance, and if the elimination pathways (gut, liver, kidney) are not ready, the body can be overwhelmed by the toxic load. This sequence has not been demonstrated in humans. That is not a sign that glutathione is bad. It is a sign that the order matters.

What this can mean in daily life: you wake up in the morning already exhausted, even though you slept nine hours. You bring the child to school, and afterwards you are done for the day. A short shopping trip feels like an ultramarathon. You have “lead in your muscles.” Your brain runs on backup mode. And the frightening part: on good days you believe things are improving, and then comes a crash that throws you back for days. That is not a failure of will, that is cell biology.

Connection to ME/CFS: 👤 Human An uncontrolled study (Wu et al. 2022, n=236 ME/CFS patients) found mycotoxins in the urine of 92.4% of participants, without a control group. Only patients with an already known history of mold exposure were included. The 92.4% are therefore not a prevalence figure for ME/CFS, they are a result of the selection. That is methodologically weak. For fibromyalgia, no such studies exist. The mechanisms (mitochondrial damage, oxidative stress, glutathione consumption) are biologically highly plausible as a contribution to both clinical pictures.

Here is the honest presentation of the facts, because I believe it is important not to create false fear, while at the same time not minimizing real risks.

What is established: 👤 Human Aflatoxin B1 (AFB1) is classified by IARC as Group 1, “carcinogenic to humans.” The mechanism is precisely worked out: AFB1 is converted in the liver to a highly reactive epoxide, binds to DNA, produces a specific mutation in the TP53 tumor suppressor gene (R249S mutation), and increases the risk of hepatocellular carcinoma. The combination with hepatitis B infection is particularly critical: the joint risk is multiplicative, not additive. AFB1 occurs mainly in foods (nuts, maize, grains in warm climates). In indoor mold in Central Europe, AFB1 is rarely the main culprit.

What is probably problematic, but not established in humans: 🐭 In vivo Ochratoxin A (IARC Group 2B) and Fumonisin B1 produce tumors in animal experiments. For humans, the evidence does not reach Group 2A or Group 1. Zearalenone, DON, and T-2 toxin are IARC Group 3, “not classifiable as to carcinogenicity.” That means the data is sufficient neither for nor against a classification. It does not mean these toxins are harmless.

What concerns me clinically is not the individual risk of a single mycotoxin, but the toxic cocktail effect. When mycotoxins arrive together with other environmental toxins (solvents, pesticides, heavy metals), chronic inflammation, and nutrient deficiencies, the sum of the load on cell division, DNA repair, and detoxification capacity could be relevant, even if no single factor by itself clearly raises the risk. This is not an alarmist scenario. But it is a reason to take avoidable chronic exposure seriously.

What this means: we are not talking about a patch of mold that causes cancer. We are talking about years of exposure with simultaneously weakened detoxification, nutrient deficiencies, and chronic inflammation, as one of many possible factors in a complex picture.

Zearalenone (ZEN) is one of the most potent known mycoestrogens, a so-called xenoestrogen, that is, a substance foreign to the body that acts like estrogen but is not estrogen. Its structure resembles natural estrogens enough that it can bind competitively to estrogen receptors (ERα and ERβ). The metabolite α-zearalenol shows an estrogenic potency three times greater than ZEN itself. 🔬 In vitro

What this can mean in the body: tissues “read” an estrogen message, but not from real estrogen, rather from a foreign substance occupying the receptors. The lab measures normal values. The body, however, behaves as if it were in estrogen dominance. And no standard lab would find ZEN in the blood, because no one is looking for it.

In rat models, ZEN induced PCOS-like states with hyperovulation, cysts, and elevated testosterone (Alenazi et al. 2024 🐭 In vivo). ZEN has been detected in human endometrial tissue. A clinical relevance for human reproduction is biologically plausible, but it has not been established in controlled human studies.

Complaints where I additionally think about a possible zearalenone exposure: menstrual cycle disturbances, intensified PMS, heavier bleeding, breast tenderness, weight gain in typical “estrogen areas,” fibroid-like complaints, endometriosis-like pain, infertility without an explainable cause. The difficult part: standard hormonal labs are often unremarkable in these cases. The tissue “experiences” estrogen activity, but the lab does not see it, because ZEN is not estrogen.

Framing the evidence: 👤 Human For the connection with human cycle disorders, PMS, or endometriosis, there are no controlled intervention studies. The estrogen-like mechanism is well established in vitro and in vivo (animal). The clinical relevance in humans remains scientifically unconfirmed, but clinically striking enough to actively ask about it when there is unclear hormonal trouble combined with a mold history.

The gut is not only a digestive organ. A very large share of the body’s immune cells sits in the intestinal lining, which makes it one of the most important immune organs. It is also the first barrier that mycotoxins must pass when ingested. That means: if you live in a moldy house, you breathe and swallow spores and toxins, and the first stop for many of these substances is the intestinal lining.

DON (deoxynivalenol) is considered a leading substance for damage to the gut barrier. In cell and animal models, DON destroys the tight-junction proteins occludin, claudin-1, and ZO-1, the molecular “rivets” that hold intestinal epithelial cells together. 🔬 In vitro🐭 In vivo When these connections loosen, the result is what is colloquially called “leaky gut,” an increased permeability that lets bacterial fragments, undigested food particles, and toxins enter the bloodstream. The immune system goes into permanent alarm.

Particularly interesting: Fan et al. (2024) showed in an animal experiment that DON-damaged gut bacteria, when transferred to healthy mice, produced the same gut problems there. In the mouse model, the altered microbiome is therefore itself part of the problem. 🐭 In vivo Whether the interaction also runs in both directions in humans, that is, whether an altered microbiome additionally worsens a mycotoxin burden, is not established.

What I see clinically again and again: 🏥 Clinical

• Paradoxical reactions: probiotics that should actually help cause bloating, pain, or worsening. That is not a sign that probiotics are bad. It could be a sign that the microbiome is so destabilized that even good bacteria trigger a dysregulated immune system.
• Stool as a barometer: bowel movements after which skin, mucous membranes, or general well-being suddenly worsen. That fits with an intestinal lining that comes into contact with toxins at every passage.
• Food intolerances appearing out of nowhere: foods that used to be problem-free now cause complaints. This is often not a true immunologic problem with the food, it is a problem of barrier integrity. When the gut wall is leaky, proteins are absorbed that would never normally reach the bloodstream.

Elimination also runs through the gut: bowel movements are one of the most important elimination pathways for mycotoxins. If someone is chronically constipated, mycotoxins that have been excreted into the gut via the bile are reabsorbed there, a toxic loop. Regular, well-formed stools are therefore not only comfort, they are a therapeutic foundation.

Framing the evidence: 👤 Human No randomized controlled human studies on the effect of indoor mycotoxins on the human gut barrier. DON is ubiquitously detectable in human body fluids from food sources. Whether indoor concentrations cause clinically meaningful barrier disruption is not proven, but the mechanistic animal models are clear.

The skin and mucous membranes are literally the interface between the inner and outer worlds. They are barrier organs, and when the inner barriers (gut, lungs) are under pressure, this often shows up first at the outermost interface: the skin.

What I notice clinically again and again: 🏥 Clinical

• Itchy, shifting rashes: not in a fixed location, but wandering. Today the forearms, next week the ankles, then suddenly the back. This wandering fits poorly into a classic dermatological pattern, and that is exactly what makes me pay attention.
• Eczema-like areas without classic atopic pattern: no family history, no typical childhood eczema, but suddenly appearing inflamed areas. They often correlate with bowel movements or with time spent in certain rooms.
• Eye burning and redness: especially after waking up (after a night in a possibly burdened bedroom), and after coming home from the office. Dry, irritated conjunctiva without infection signs.
• Chronic sinusitis: recurring blocked sinuses, persistent mucus production. What if the nasopharynx is in direct contact with a mold reservoir in the air-conditioning or the walls?

The skin is the first organ that shows when the immune system, the barriers, and detoxification reach their limits. That is biologically meaningful: the body tries to clear excess toxins and inflammatory products through the skin as well. What looks like a skin problem is sometimes a detoxification problem.

What is best documented here: 👤 Human For allergic respiratory diseases, asthma, and rhinitis in connection with indoor mold, there are meta-analyses drawing on numerous individual studies. This is the best established part of the mold-and-health connection. A widely quoted US estimate (Mudarri and Fisk, Indoor Air 2007, taken up by the WHO in 2009) arrives at a share of about 21 percent of asthma there that could be linked to indoor dampness and mold. The figure applies to the USA and cannot simply be transferred to Germany. A meta-analysis of 31 studies (Jaakkola et al., J Allergy Clin Immunol 2013) found, with visible mold, an increased risk for rhinitis overall (OR 1.82) and for allergic rhinitis (OR 1.51). The association was strongest with a musty odor.

For the other skin manifestations, the wandering eczemas and inflammatory rashes, there are no controlled human studies with mold exposure. The clinical pattern is, however, consistently described in environmental medicine.

What keeps showing up without the cardiological work-up finding anything: 🏥 Clinical

• Palpitations without findings: palpitations that suddenly appear, on standing up, after meals, sometimes at night. The ECG is unremarkable, the Holter monitor only shows “sinus tachycardia under stress.” But why does someone have permanent “stress” in the heart, even on holiday?
• Dizziness when standing: what conventional medicine describes as “orthostatic dysregulation” or mild POTS-like symptoms. Blood pools downward when standing, the heart has to pump harder, and the head briefly gets too little perfusion. In some people with mold exposure, this could be tied to autonomic dysregulation, the autonomic nervous system has been thrown out of its regulatory range by chronic exposure.
• Temperature chaos: alternating between feeling cold and having hot flashes. Cold in the morning, hot in the afternoon, cold again in the evening. That fits an autonomic nervous system that can no longer hold thermoregulation steady, because it is overloaded with other regulatory loops.
• Daily crashes: you have a good hour in which you think this will be a productive day. Then comes the crash. Suddenly all the energy is gone, the head heavy, the muscles powerless. As if someone had flipped a switch. That is not imagination, it is a metabolic collapse at the cellular level.

In the KPNI framework, this gives a coherent picture: the autonomic nervous system, sympathetic (gas) and parasympathetic (brake), is the conducting system of the body. When mycotoxins irritate the immune system, weaken the mitochondria, and put the nervous system into permanent alarm, the autonomic nervous system loses its flexibility. It can no longer switch quickly between activity and recovery. This is called low heart rate variability (HRV). I see it often in people with a long chronic burden. The finding is unspecific, it occurs with many chronic burdens, and it does not prove mold exposure. 🏥 Clinical

The result feels like: “My body is constantly at 130%, without me doing anything big.” Not because you are weak, but because your system is fighting on several levels at the same time and can no longer find a real recovery mode.

Framing the evidence: for autonomic dysregulation through mycotoxins, no direct human studies exist. The mechanism via neuroinflammation leading to autonomic dysregulation is biologically well grounded, but it has not been specifically demonstrated in humans through mold exposure.