Happy Mold vs Angry Mold: A Problem of Mycotoxins Part I

 

Mycotoxins—toxic secondary metabolites produced by certain molds—represent one of the most underrecognized threats to human health in modern society. While many people are aware of mold allergies, few understand that the real danger often lies not in the mold itself, but in the powerful biological toxins these fungi produce as chemical weapons. These compounds, evolved over millions of years as fungal defense mechanisms, can wreak havoc on human physiology at remarkably low concentrations.

Why “happy mold” and “angry mold”? Mold is a normal part of the natural world. Outdoors, in soil and on fallen leaves, it lives in balance with everything around it and rarely needs its chemical weapons. That is happy mold. Put the same mold inside a water-damaged building and it behaves very differently. It has all the food and moisture it needs, and it is crowded by bacteria and other molds competing for the same damp drywall. Making toxins costs a mold a lot of energy; here it has both the energy and the reason to make them. That is angry mold. This series is about the angry kind: what it produces, how those toxins reach and affect the body, and, in Part II, what to do about it.

What Are Mycotoxins?

Mycotoxins are molecules with diverse polarity, many of which are lipophilic (fat-loving) compounds with molecular weights of a few hundred daltons, making them small enough to penetrate biological barriers with ease. While over 400 mycotoxins have been identified, only a handful regularly contaminate our food supply and indoor environments. I describe the major ones, and how each acts, further down.

Importantly, mycotoxins are not essential for fungal growth or reproduction. Rather, they serve as biological warfare agents—protecting the mold colony from competing organisms, insects, and animals that might otherwise consume them. This explains why these compounds are so profoundly toxic to biological systems: they were literally designed by evolution to disrupt life processes.

Internal Mycotoxin Production: A Hidden Threat

A particularly insidious aspect of mycotoxin exposure is that we can actually produce these toxins inside our own bodies when we have fungal colonization. When mold species like Aspergillus or Candida colonize the sinuses or gastrointestinal tract, they don't just sit there passively—they actively produce mycotoxins directly within our tissues.

This means that even after leaving a water-damaged building, individuals with sinus or gut colonization continue to have ongoing mycotoxin exposure from internal sources. Gliotoxin, for instance, is produced not only by Aspergillus fumigatus when it colonizes the gut and/or sinuses, and in extreme cases the lungs, but also by Candida species which often colonize the gut/sinuses. This internal production can perpetuate symptoms and inflammation long after environmental exposure has ceased, making treatment more complex and extended.

The discovery of internal mycotoxin production helps explain why some individuals remain symptomatic despite environmental remediation—the "mold problem" has become an internal one, requiring targeted antifungal treatment and biofilm disruption protocols in addition to standard mycotoxin detoxification approaches.

The Modern Mycotoxin Crisis: Why Exposure Is Escalating

Water-Damaged Buildings: Creating "Angry Mold"

Research has revealed a critical difference between mold in its natural outdoor habitat versus mold growing in water-damaged buildings. In nature, most molds exist in ecological balance, rarely producing significant quantities of mycotoxins. However, when molds colonize indoor environments—particularly water-damaged buildings—the conditions trigger aggressive mycotoxin production.

Understanding Water Activity and Building Materials

Fungal growth depends on water activity (aw)—a measure of available moisture on a scale from 0 (bone dry) to 1.0 (pure water). For perspective, materials like drywall or wood at aw 0.80 have a moisture content around 16%, while aw 0.90 corresponds to roughly 20% moisture content. This matters because building materials don't need to be visibly wet or saturated to support mold growth.

Studies show that common indoor molds like Aspergillus and Penicillium begin to grow at a water activity near 0.8—moisture levels that feel merely "damp" to the touch or may not be obvious at all. Significant mycotoxin production needs a water activity of about 0.95 (Nielsen, 2003), though optimal conditions vary by species and toxin type. The worst-case scenario involves cycles of water damage that promote fungal growth and mycotoxin synthesis, followed by drier conditions that facilitate the liberation of spores and hyphal fragments carrying concentrated mycotoxins.

Research on water-damaged buildings has found mycotoxins in a substantial share of bulk samples from moisture-damaged materials; one key study found sterigmatocystin in 24% and trichothecenes in 19% of samples. Aspergillus and Penicillium species are among the most common primary colonizers in water-damaged buildings, quickly establishing themselves on damp surfaces. Stachybotrys species, while often called "black mold" in popular media, are actually tertiary colonizers that appear after Aspergillus and Penicillium have established themselves. However, when Stachybotrys does colonize, it generates extraordinarily high quantities of chemically distinct metabolites—particularly the highly toxic macrocyclic trichothecenes. These metabolites are carried by spores at concentrations detectable in air samples. Sterigmatocystin from Aspergillus versicolor can accumulate to high levels under very wet conditions.

It's Not Just Mold: Actinomycetes and Endotoxins

An ecosystem, not a single organism. A water-damaged building is an unnatural ecosystem. Outdoors, limited water and food keep mold and bacteria in a natural balance. Indoors, with steady moisture and plenty to eat, they multiply side by side and begin to compete. Mold makes mycotoxins on purpose, as weapons to defend and expand its territory against other molds and bacteria. It is not trying to harm people, but the same mechanisms that damage bacteria and other fungi damage us. We are bystanders who happen to be living in a biological war zone. The bacteria add to it without meaning to: actinomycetes give off metabolites that act like antibiotics, and gram-negative bacteria release endotoxin as they die. Because the mix of molds, bacteria and toxins differs from one building to the next, with possible combinations running into the millions, no two sick buildings are alike, and neither are the people living in them.

A water-damaged building isn't only a mold problem. As Dr. Neil Nathan puts it, what grows behind the wall is an "inflammatory soup": mold spores and fragments, mycotoxins, beta-glucans and other cell-wall pieces, gases released by microbes (MVOCs), and two groups of bacteria that are easy to overlook: actinomycetes and the gram-negative bacteria that shed endotoxins. Dr. Jill Crista estimates that roughly a third of people who stall in mold recovery need these addressed as well.

Actinomycetes are gram-positive bacteria, most at home in soil. Most are harmless (the same wider group includes beneficial gut bacteria), but some strains become pathogenic and form biofilms. They feed on chitin, the material that makes up fungal cell walls, so a moldy building is a buffet for them. And when actinomycetes chew on mold, the mold responds by producing more mycotoxin. Many of our antibiotics were originally isolated from actinomycetes, and breathing in their metabolites day after day can disrupt the microbiome of the gut, skin and sinuses and encourage yeast overgrowth.

• Where they grow: gray- or black-water leaks, rotting wood, dirt crawl spaces and basements, drain traps, litter boxes, and houseplants whose soil has "turned"
• A building can be sick without visible mold if the problem started with a drain or sewer issue
• People can become their own source, shedding actinomycetes onto bedding and clothing, which is why some people feel better in a new place for a couple of weeks and then decline again

Endotoxins (lipopolysaccharide, or LPS) are pieces of the outer wall of gram-negative bacteria, released when those bacteria die. They thrive wherever water sits: sewer backups, toilet overflows, pet urine, and water-holding devices such as CPAP machines, humidifiers, water flossers, coffee machines and old nasal-spray bottles. Endotoxins suppress bile formation, which makes mycotoxins harder to clear, and inhaled endotoxin primes the brain's immune cells toward inflammation. They also come from inside the body, from a dysbiotic gut, the sinuses or the lungs, so they are both an environmental and an internal load.

Clues that actinomycetes or endotoxins are part of the picture (from Dr. Crista):

• Itchy red-dot rashes, heat hives, swollen eyelids
• Acne, rosacea and rashes around the nose and eyes; pustules in the armpits or groin
• Chronic sinus or lung infections
• Dysbiosis, SIBO or food sensitivities that persist despite good treatment
• Mast cell reactivity
• Bladder or prostate irritation
• Flu-like achiness after exertion

A few more clues: Chlamydia pneumoniae and Mycoplasma infections turn up often in people from water-damaged buildings (Dr. Marie Matheson), and the source isn't always the home. A workplace, a church or a CPAP machine can be the culprit. Many molds also produce oxalates, which can tip someone into oxalate problems they never had before (Dr. Nathan).

An Emerging Connection: Electromagnetic Fields and Mycotoxin Production

Emerging research has explored whether electromagnetic fields (EMFs) might influence fungal behavior and mycotoxin production, though this area remains controversial and requires more peer-reviewed research. Dr. Dietrich Klinghardt has reported experiments where mold cultures shielded from ambient EMFs in a Faraday cage produced baseline levels of mycotoxins, but when exposed to laboratory EMFs (from lights, computers, and cell phone radiation), mycotoxin production increased dramatically—potentially by several hundred-fold.

Lab research has found that radiofrequency electromagnetic field (RF-EMF) exposure at 2 GHz increased enzyme production in Aspergillus oryzae, suggesting EMFs can indeed alter fungal metabolism. While the exact mechanisms and extent of EMF effects on mycotoxin production require further investigation, the hypothesis is that molds may perceive electromagnetic fields as environmental stressors, triggering defensive mycotoxin production.

Given the exponential increase in EMF density in our environment over the past two decades—from Wi-Fi routers, cell phones, smart meters, and 5G technology—this potential connection warrants serious scientific investigation. If confirmed, it would mean that our modern technological environment is inadvertently creating more aggressive, toxic molds in our buildings.

The Food Connection: From Field to Fork

Agricultural Contamination

Mycotoxins are also in our food supply, and some exposure is nearly unavoidable, even on a healthy diet. Climate conditions, particularly warm and humid weather, favor mycotoxin production in crops. Globally, up to 60–80% of food crops contain detectable mycotoxins, and about 25% exceed regulatory limits.

That said, in my clinical experience environmental exposure is far more relevant than food for the people I work with, and Dr. Neil Nathan sees the same: the vast majority of mold toxicity in his patients traces back to water-damaged buildings, not diet. Food still matters, and coffee and grains (a source of citrinin) are notable exceptions, but the building usually comes first.

Grains represent the highest risk category:

• Corn/Maize: Frequently contaminated with aflatoxins, fumonisins, deoxynivalenol, and zearalenone. Studies show up to 100% contamination rates for fumonisins in some regions.
• Wheat: Primary concern for deoxynivalenol (DON) from Fusarium head blight. Surveys in some regions have found DON in a large share of wheat samples.
• Rice: Can contain aflatoxins, ochratoxin A, fumonisins, trichothecenes, and zearalenone.
• Oats, Rye, and Barley: Susceptible to various Fusarium mycotoxins and ergot alkaloids (especially rye).

Other high-risk foods include:

• Nuts (peanuts, pistachios, almonds, walnuts) - aflatoxins
• Coffee - ochratoxin A
• Wine and beer - ochratoxin A
• Dried fruits - aflatoxins, ochratoxin A
• Spices (chili peppers, black pepper, turmeric) - aflatoxins
• Oils (corn, peanut) - aflatoxins

Mineral Depletion and Plant Susceptibility

Modern agricultural practices have led to significant mineral depletion in soils, weakening plants' natural defense mechanisms. When plants lack essential minerals and are under stress, they become more susceptible to fungal infection. Fusarium species, in particular, thrive on weakened, mineral-depleted crops.

Compounding this problem, many pesticides function as chelators—chemicals that bind to and sequester minerals. These pesticides not only fail to remineralize depleted soils but actively leach minerals out of both the soil and the plants themselves. This dual assault—lack of soil remineralization combined with pesticide-induced mineral chelation—creates profoundly compromised crops.

This creates a vicious cycle: depleted soils treated with mineral-chelating pesticides produce severely compromised plants that are more easily colonized by toxigenic fungi, which then contaminate our food supply with mycotoxins. The emphasis on high-yield agriculture without adequate soil remineralization, combined with heavy pesticide use, has inadvertently increased our mycotoxin exposure through the food chain.

From Animal Feed to Human Food

The discovery of mycotoxin binders—substances that prevent mycotoxin absorption—emerged from veterinary medicine when researchers sought to protect livestock from mycotoxin-contaminated feed. When animals consume grain-based feeds contaminated with mycotoxins, they can develop serious health problems, including reduced growth, immune suppression, reproductive issues, and even death.

Veterinarians and animal nutritionists developed various binders to protect livestock health. In laboratory tests, averaged across several toxins, they adsorbed (Kihal et al., 2022):

• Activated carbon (83% average adsorption capacity)
• Montmorillonite clay (76% adsorption)
• Bentonite (62% adsorption)
• Hydrated sodium calcium aluminosilicate (HSCAS) (55% adsorption)
• Zeolites clinoptilolite (52% adsorption)
• Yeast cell wall products (44% adsorption)

These binders work through various mechanisms—chemical interactions (ion-dipole bonds, Van der Waals forces, hydrogen bonding) and physical characteristics (pore size matching mycotoxin structure). The success of mycotoxin binders in animal agriculture demonstrated that mycotoxins could be intercepted in the gastrointestinal tract, a principle now applied to human mycotoxin detoxification protocols.

How Mycotoxins Enter and Damage the Body

Routes of Exposure

Mycotoxins are remarkably efficient at entering the human body through multiple pathways:

1. Inhalation: The most direct and dangerous route in water-damaged buildings. Mycotoxins attach to fine fragments smaller than spores, many under 1 micrometer, which can:

• Penetrate deep into the respiratory system
• Lodge in the nasal passage and migrate through the cribriform plate—a thin bone separating the nasal cavity from the brain—via olfactory nerves directly into the olfactory bulb and brain, bypassing the blood-brain barrier entirely
• Travel along trigeminal nerves to reach the brainstem
• Enter the bloodstream through lung tissue
• Be cleared by ciliated cells in the respiratory tract and subsequently swallowed, where they then damage the gastrointestinal lining—meaning inhaled mycotoxins can cause gut damage indirectly through this mucociliary clearance mechanism

2. Ingestion: Through contaminated food and beverages, mycotoxins are absorbed through the gastrointestinal tract, causing direct damage to the gut lining.

3. Dermal Absorption: T-2 toxin and other lipophilic mycotoxins can be absorbed through skin contact with contaminated materials.

Mechanisms of Cellular Damage

Mycotoxins exert their devastating effects through multiple biochemical mechanisms:

Mitochondrial Dysfunction and Oxidative Stress: The lipophilic nature of mycotoxins allows them to easily penetrate cell membranes and accumulate in lipid-rich tissues, particularly the brain (which is ~60% fat), liver, and adipose tissue. Once inside cells, mycotoxins:

• Disrupt mitochondrial electron transport chains, leading to excessive reactive oxygen species (ROS) production
• Inhibit mitochondrial protein synthesis
• Damage mitochondrial DNA
• Activate mitochondrial permeability transition, releasing pro-apoptotic factors like cytochrome c
• Impair cellular energy production (ATP synthesis)
• Directly deplete glutathione, our bodies' master antioxidant
• Trigger oxidative damage to lipids, proteins, and DNA

Studies show that trichothecene mycotoxins specifically target mitochondria, creating a vicious cycle: initial mitochondrial damage leads to increased ROS production, which causes further mitochondrial dysfunction. This oxidative cascade can overwhelm cellular antioxidant defenses, leading to cell death.

Protein Synthesis Inhibition: Many mycotoxins, particularly trichothecenes, bind to ribosomes and inhibit protein synthesis. Deoxynivalenol (DON), for example, interacts with the peptidyl transferase enzyme on the 60S ribosomal subunit, blocking translation. This "ribotoxic stress" activates mitogen-activated protein kinases (MAPKs), triggering inflammation, apoptosis, and immune dysregulation.

Inflammatory Cascade Activation: Mycotoxins stimulate the production of pro-inflammatory cytokines, including:

• Tumor Necrosis Factor-alpha (TNF-α)
• Interleukin-1 beta (IL-1β)
• Interleukin-6 (IL-6)
• Interleukin-8 (IL-8)

This chronic inflammation contributes to tissue damage throughout the body and is particularly problematic when mycotoxins cross into the brain, where neuroinflammation can lead to cognitive dysfunction and neuropsychiatric symptoms.

Albumin Binding and Systemic Distribution: Some mycotoxins have an unusual ability to bind to plasma proteins, especially albumin. Both aflatoxins and ochratoxin A demonstrate this characteristic, which profoundly affects their toxicokinetics. This binding:

• Extends their half-life in the body dramatically (ochratoxin A has a half-life of ~35 days due to tight albumin binding)
• Allows them to circulate systemically, causing oxidative damage throughout the body as they remain bound to serum proteins
• Makes them more difficult to eliminate through normal detoxification pathways
• Creates a "reservoir" effect where bound mycotoxins are slowly released over time

The Major Mycotoxins and How They Act

Much of the detail below is drawn from Dr. Jill Crista’s teaching, alongside the published research. The major mycotoxins of concern include:

1. Aflatoxins (AFB1, AFB2, AFG1, AFG2, AFM1) - Produced by Aspergillus flavus and A. parasiticus, these are among the most potent natural carcinogens known to science. The liver’s own enzymes convert aflatoxin B1 into a reactive form that binds DNA, and liver cancers from high-exposure regions carry its signature mutation (Guengerich et al., 1996; Hsu et al., 1991)
2. Ochratoxin A (OTA) - Produced by Aspergillus and Penicillium species, known for kidney toxicity. It blocks protein synthesis and damages mitochondria (Ringot et al., 2006), and it binds the blood protein albumin so tightly that less than 0.2% circulates free (Hagelberg et al., 1989), so the kidneys barely filter it and it lingers
3. Trichothecenes - Including T-2 toxin, HT-2 toxin, and deoxynivalenol (DON), produced mainly by Fusarium species. They bind the ribosome, stop protein synthesis and set off a stress response that drives inflammation and cell death (Pestka, 2010). DON, also called vomitoxin, causes vomiting and appetite loss and weakens the gut barrier (Pinton & Oswald, 2014). They are active on contact and can be absorbed through the skin and eyes
4. Macrocyclic Trichothecenes - Including satratoxins, roridins and verrucarins from Stachybotrys chartarum (black mold) and Trichoderma. These are the most toxic of the family: in mice and monkeys, satratoxin G placed in the nose killed the nerve cells for smell and inflamed the nose and brain (Islam et al., 2006; Carey et al., 2012)
5. Fumonisins (FB1, FB2, FB3) - Produced by Fusarium species, particularly F. verticillioides. They block ceramide synthase, which disrupts the sphingolipids that cell membranes and nerve sheaths are built from (Wang et al., 1991), and they interfere with folate transport; where contaminated maize is a staple, they are linked to neural tube defects (Missmer et al., 2006)
6. Zearalenone (ZEA) - An estrogenic mycotoxin from Fusarium species. It binds both estrogen receptors at very low concentrations (Kuiper et al., 1998), and the body converts part of it into an even more estrogenic form
7. Citrinin - Produced by Penicillium and Aspergillus species. A kidney toxin often found alongside ochratoxin A that acts on the mitochondria (Flajs & Peraica, 2009); it can show up as frequent urination and fatigue with muscle pain
8. Gliotoxin - Produced by Aspergillus fumigatus and Candida species, often internally. Its sulfur bridge reacts with proteins and generates free radicals, shuts down the immune switch NF-κB and kills immune cells (Gardiner et al., 2005; Pahl et al., 1996), which opens the door to fungal infection
9. Patulin - Found in rotting apples and other fruits; produced by Penicillium and Aspergillus. It reacts with sulfur (thiol) groups; in human gut cells it weakened the barrier within hours, and glutathione protected against it (Mahfoud et al., 2002)
10. Sterigmatocystin - Produced by Aspergillus versicolor, a precursor to aflatoxin. It has a similar structure, damages DNA, and is toxic to the liver and kidney in animals (Zingales et al., 2020)
11. Chaetoglobosins (especially chaetoglobosin A) - Produced by Chaetomium globosum, one of the most common molds on water-damaged drywall and wood. Chaetoglobosins bind actin, the protein scaffolding inside every cell, so they can halt cell division (the cell cycle) and stop cells from moving and repairing. Actin is also the contractile backbone of muscle, which makes muscle weakness and pain a plausible effect, and it is what holds the cells lining our blood vessels tightly together: in lab studies, actin-disrupting compounds made the vessel lining two to three times more permeable, a potential route to leaky, inflamed vessels
12. Mycophenolic acid (MPA) - Produced by Penicillium species. Strictly a mold metabolite rather than a classic mycotoxin, but a powerful immune suppressant that blocks the multiplication of immune cells (more on this below)
13. Enniatins (especially enniatin B) - Produced by Fusarium species and common in cereal grains. They act as ionophores, punching holes in cell and mitochondrial membranes (Tonshin et al., 2010), and can cross the blood-brain barrier, as shown in mice (Taevernier et al., 2016)

Mycophenolic Acid: Mold’s Immune Suppressant

Mycophenolic acid (MPA) is made by Penicillium species; one of them, P. brevicompactum, grows on damp building materials and can produce it there (Nielsen et al., 1999). It works by blocking IMPDH, an enzyme that dividing cells need to make the building blocks of DNA. T and B lymphocytes depend on that enzyme more than other cells do, so at very low concentrations MPA stops them from multiplying (Eugui et al., 1991). It is so potently immunosuppressive that a synthetic derivative (mycophenolate mofetil) is used pharmaceutically to prevent organ transplant rejection.

For someone living in a moldy building, that matters. Dr. Jill Crista links MPA to infections of all kinds, low secretory IgA, colonization of the mucosal surfaces and damage to the gut lining. As she puts it, “Where there is living mold, there is MPA.” It also clears quickly once exposure ends, so both she and Dr. Neil Nathan read a persistently high MPA result as a sign of ongoing exposure.

Systemic Health Consequences

Gut Barrier Dysfunction ("Leaky Gut")

Mycotoxins are particularly damaging to the intestinal epithelium. Research shows that deoxynivalenol (DON) causes:

• Decreased expression of tight junction proteins (claudins, occludin, ZO-1)
• Loss of barrier function
• Increased intestinal permeability ("leaky gut")
• Enterocyte apoptosis

When the gut barrier is compromised, partially digested food particles, bacteria, and toxins can enter the bloodstream, triggering systemic immune activation and chronic inflammation. This gut damage also impairs nutrient absorption and disrupts the microbiome, creating a cascade of metabolic and immune problems.

Zearalenone (ZEA), in particular, alters gut microbiota composition and can induce gut dysbiosis. The estrogenic properties of ZEA combined with gut barrier disruption create conditions favorable for chronic inflammatory diseases.

Adipose Tissue Inflammation and Endocrine Disruption

Mycotoxins' lipophilic nature means they accumulate in fat tissue, where they can remain for extended periods. This accumulation has profound metabolic consequences:

Estrogenic Effects: Zearalenone is a non-steroidal estrogenic mycotoxin that mimics estrogen in the body. It binds to estrogen receptors, causing:

• Hormonal imbalances affecting reproductive health
• Increased risk of estrogen-sensitive conditions (endometriosis, certain cancers)
• Disrupted menstrual cycles and fertility in women
• Feminization effects in men (gynecomastia, reduced testosterone), seen so far in animal studies

Adipose Tissue Inflammation: When mycotoxins accumulate in adipose tissue, they trigger local inflammation characterized by:

• Macrophage infiltration
• Production of pro-inflammatory cytokines
• Altered adipokine secretion (decreased adiponectin, increased leptin)
• Increased production of inflammatory mediators

This inflamed adipose tissue becomes metabolically dysfunctional, contributing to:

• Insulin resistance
• Metabolic syndrome
• Systemic inflammation
• Difficulty losing weight (as stored mycotoxins are released during fat metabolism, triggering additional inflammation)

Moreover, inflamed adipose tissue shows increased aromatase expression, converting androgens to estrogens and creating a state of estrogen dominance. This estrogenic environment further promotes inflammation and metabolic dysfunction.

Respiratory and Airway Damage

Inhalation of mycotoxins causes direct damage to the respiratory system:

• Inflammation of nasal passages and sinuses
• Chronic sinusitis often refractory to standard treatments
• Olfactory neuron loss and dysfunction
• Lung inflammation and fibrosis
• Exacerbation of asthma and allergic airways disease
• Chronic cough and respiratory symptoms

Studies on macrocyclic trichothecenes from Stachybotrys show they cause significant olfactory sensory neuron loss and inflammation in both the nasal airways and brain tissue.

Airway mycosis. Dr. David Corry's research group at Baylor College of Medicine has shown that fungi don't only trigger allergies from the outside; they can grow on the airway surface itself, a low-grade infection they call airway mycosis. In one study, filamentous fungi were cultured from the airways of 74% of people with chronic Th2-driven airway disease (asthma, chronic rhinosinusitis with nasal polyps and allergic fungal sinusitis), compared with 16% of people with other airway conditions. In asthma patients with culture-proven airway mycosis, antifungal treatment improved asthma control and lung function and roughly halved IgE levels.

Hypersensitivity pneumonitis. Both mold and actinomycetes can cause hypersensitivity pneumonitis, an immune-driven inflammation of the small airways and air sacs of the lungs. The classic example, farmer's lung, is caused by thermophilic actinomycetes (Saccharopolyspora rectivirgula) in moldy hay, and many fungi, in homes and workplaces as well as on farms, cause it too.

MARCoNS and Chronic Mucosal Barrier Dysfunction

A particularly insidious consequence of mycotoxin exposure is the development of MARCoNS (multiple antibiotic-resistant coagulase-negative staphylococci) in the nasal passages. These antibiotic-resistant bacteria colonize damaged sinus tissue and produce exotoxins that further suppress the immune system. As Dr. Jill Crista puts it, "If there's MARCoNS or MRSA, there's a smarter fungus underneath", so MARCoNS is best seen as a marker pointing to fungal colonization and biofilm beneath it, rather than the main target on its own.

The connection to broader health impacts occurs through disruption of Alpha Melanocyte-Stimulating Hormone (alpha-MSH). Mycotoxin exposure damages the hypothalamic neurons that produce Pro-opiomelanocortin (POMC), the precursor molecule that gets cleaved into multiple important peptides including MSH, endorphins, and ACTH. When POMC neurons are damaged, MSH production plummets.

Low MSH has cascading effects throughout the body:

Mucosal Barrier Dysfunction

• MSH is critical for maintaining the integrity of all mucosal barriers (sinuses, gut, lungs, bladder)
• Low MSH leads to chronic sinus infections (enabling MARCoNS colonization)
• Contributes to gut permeability and chronic gastrointestinal issues
• MSH is strongly anti-inflammatory - its loss removes the brake on inflammation
• Increases susceptibility to recurrent infections across all mucosal surfaces

Melanin, MSH, and Neurodegeneration

α-MSH (derived from POMC) does more than regulate mucosal immunity—it also signals through melanocortin receptors such as MC1R, which are found in dopaminergic neurons of the substantia nigra, the region most affected in Parkinson’s disease. Through these receptors, α-MSH helps modulate antioxidant and anti-inflammatory defenses in the brain.

In the substantia nigra, neuromelanin forms mainly from the oxidation of dopamine rather than from the skin-type, tyrosinase-driven pathway. Even so, neuromelanin functions as a protective biopolymer - it binds metals like iron, manganese and copper, scavenges free radicals, and buffers oxidative stress in these highly active neurons.

If chronic inflammation or toxin exposure lowers α-MSH output, melanocortin signaling and neuronal resilience may be weakened. Combined with direct mycotoxin neurotoxicity, neuroinflammation, and mitochondrial stress, this loss of signaling could heighten vulnerability in dopaminergic neurons.

This mechanism may help explain why mold illness specialists are increasingly observing Parkinsonian symptoms and early neurodegenerative changes in chronically mold-exposed patients. The combination of:

• Direct mycotoxin neurotoxicity
• Chronic neuroinflammation, and loss of anti-inflammatory MSH brake
• Decreased melanin-based neuroprotection and increased oxidative stress from unbound metals
• Mitochondrial dysfunction and glutathione depletion

...creates a perfect storm for neurodegeneration, particularly in the vulnerable dopaminergic neurons of the substantia nigra.

Neurological and Neuropsychiatric Effects

The brain is particularly vulnerable to mycotoxin toxicity due to its high lipid content and extraordinary metabolic demands. Mycotoxins can reach the brain via:

• Crossing the blood-brain barrier (especially lipophilic mycotoxins like beauvericin and enniatins)
• Direct transport through the cribriform plate via olfactory nerves
• Transport along trigeminal nerves

Once in neural tissue, mycotoxins cause:

Cognitive Impairment

• Brain fog and difficulty concentrating
• Short-term memory loss
• Impaired executive function
• Slowed processing speed
• Difficulty with word-finding and verbal fluency
• Hypothalamic inflammation and damage affecting hormonal and neurotransmitter patterns (MSH, VIP, melatonin, leptin)

Neuropsychiatric Symptoms: The connection between mycotoxins and mental health is increasingly recognized. Specific associations include:

• Depression: Linked to ochratoxin A, trichothecenes and aflatoxins. Large population studies link damp, moldy homes to depression (Shenassa et al., 2007), and mood changes and despair are associated with gliotoxin in particular.
• Anxiety: Associated with multiple mycotoxins, particularly through their effects on mast cell activation and inflammatory cytokine production.
• Mood Instability and Irritability: Common with chronic mycotoxin exposure, likely related to neuroinflammation and disrupted neurotransmitter metabolism.
• Psychosis and Hallucinations: Fungal toxins have a long history here: ergot alkaloids from a fungus that infects rye caused repeated epidemics of "ergotism" (St. Anthony's fire) in medieval Europe, with hallucinations and convulsions. LSD was first made from an ergot compound. Modern case reports link Stachybotrys exposure to psychotic symptoms.
• Dark or Suicidal Thoughts: Large population studies link damp, moldy homes to depression, and in my practice some mold-exposed clients describe dark, intrusive or suicidal thoughts that ease as their exposure and inflammation come down. Inflammation itself is part of this picture: people experiencing suicidal thoughts show higher levels of the inflammatory messengers IL-1β and IL-6 in their blood and brain tissue. If you're having thoughts of suicide, you can call or text 988 (Suicide & Crisis Lifeline, US) any time. In Canada, call or text 9-8-8.
• Autism Spectrum Disorder: Emerging research shows children with autism have differences in some urinary and blood mycotoxin levels compared to neurotypical peers, suggesting a possible environmental trigger or exacerbating factor.
• Neurodegenerative Diseases: Dr. Dale Bredesen has identified an "inhalational Alzheimer's disease" subtype associated with mycotoxin exposure. Fungi may also play a role in amyotrophic lateral sclerosis (ALS) and Parkinson's disease pathogenesis.

The mechanisms underlying these neuropsychiatric effects include:

• Neuroinflammation mediated by microglial activation
• Mast cell activation releasing pro-inflammatory mediators in the brain
• Disruption of neurotransmitter synthesis and metabolism
• Mitochondrial dysfunction in neurons
• Oxidative damage to neural tissue
• Impaired neuroplasticity

Mold Gases (MVOCs) and the Brain

Molds also release gases, called microbial volatile organic compounds (MVOCs). They are what you smell as mustiness; mycotoxins themselves have no odor. The best studied is 1-octen-3-ol, or “mushroom alcohol”. In fruit flies it lowered dopamine and caused loss of dopamine neurons and movement problems, and in human cells it blocked dopamine uptake (Inamdar et al., 2013). In one rat study, inhaling it worsened depressive-like behavior and lowered serotonin and norepinephrine (Song et al., 2025). These are animal and cell findings at experimental doses; the gases in homes have not yet been studied this way in people. Dr. Marie Matheson associates mold gases and aldehydes with visual problems, headaches, tinnitus, brain fog and fatigue.

Why Individual Responses Vary: The Genetics and Hormones of Mycotoxin Sensitivity

A critical question emerges: Why do some people develop severe illness from mold exposure while others seem unaffected? The answer lies in genetics, detoxification and hormonal status.

The HLA-DR Gene and Biotoxin Illness

Dr. Ritchie Shoemaker estimates that about a quarter of people carry genetic variants in the Human Leukocyte Antigen (HLA) system—specifically HLA-DR and HLA-DQ genes—that have been proposed to impair their ability to recognize and eliminate mycotoxins. These HLA genes are part of the immune system's major histocompatibility complex, responsible for presenting antigens to immune cells.

Certain HLA-DR/DQ haplotypes (gene combinations) are associated with increased susceptibility to Chronic Inflammatory Response Syndrome (CIRS) from biotoxins. Individuals with these susceptibility genes:

• May mount weaker immune responses to mycotoxins
• May clear mycotoxins less efficiently from their bodies
• Experience prolonged mycotoxin retention and accumulation
• Are more likely to develop severe, persistent symptoms

Clinical reports on mold-exposed individuals with HLA-DR variations describe very slow elimination of mycotoxins such as ochratoxin A, which can stay detectable long after exposure ends. This slow clearance transforms even short-term exposure into a chronic exposure scenario with related adverse health effects.

That said, HLA-DR now appears to be less important than once thought. In his clinical work, Dr. Neil Nathan has seen no correlation between HLA-DR type and how well people recover, and anyone can become mold-toxic with enough exposure. HLA-DR is best seen as one possible piece of the susceptibility puzzle, not a verdict.

Detoxification Pathway Genetics

Beyond HLA genes, genetic variants in detoxification pathways affect mycotoxin metabolism:

Phase I Detoxification (Cytochrome P450 enzymes)

• CYP1A1, CYP1A2, CYP1B1, CYP3A4 variants affect aflatoxin and ochratoxin metabolism
• Some variants increase toxic metabolite formation

Phase II Detoxification (Conjugation)

• Glutathione S-transferase (GST) variants affect mycotoxin conjugation
• GSTM1 and GSTT1 null genotypes are associated with reduced detoxification capacity
• UDP-glucuronosyltransferase (UGT) variants affect mycotoxin elimination

Hormonal Influences on Mycotoxin Sensitivity

Beyond genetics, hormonal status plays a crucial role in determining mycotoxin sensitivity, particularly through effects on mast cell activity:

Testosterone: A Protective Factor: Testosterone exerts protective effects against mast cell activation syndrome (MCAS):

• Stabilizes mast cells, making them less prone to degranulation
• Reduces histamine release
• Modulates inflammatory responses
• May explain why men often have lower rates of MCAS and histamine-related symptoms

Estrogen: Increasing Mast Cell Reactivity: Estrogen has the opposite effect:

• Promotes mast cell activation and easier degranulation
• Increases histamine synthesis and release
• Enhances inflammatory responses
• Explains why women (especially during high-estrogen phases) are more susceptible to MCAS
• May contribute to the higher prevalence of mold illness symptoms in women

This hormonal dynamic helps explain several clinical observations:

• Women often experience more severe histamine-related symptoms from mycotoxin exposure
• Symptoms may fluctuate with menstrual cycle (worse during high-estrogen phases)
• Perimenopausal and menopausal women may experience changes in symptom severity as hormone levels shift
• Men with low testosterone may be more susceptible to mold-related MCAS symptoms
• Exposure to estrogenic mycotoxins like zearalenone compounds the problem by adding exogenous estrogen-like effects on top of endogenous estrogen

I cover mast cells in depth in Mast Cells: When Your Body Reacts to Everything, and the estrogen side of this in When Estrogen Steals the Show.

Other Susceptibility Factors

• Gut health status
• Nutritional status (particularly antioxidants and minerals)
• Chronic stress and cortisol levels
• Concurrent exposures to other toxins
• Mold colonization in sinuses or gut

The Universal Nature of Mycotoxin Toxicity

While genetic and hormonal factors influence susceptibility, it's crucial to understand that mycotoxins affect everyone. The immune response to mold exposure occurs along multiple pathways:

• Some people mount IgE-mediated allergic responses to mold spores (classic allergy with histamine release, sneezing, itching)
• Others respond primarily through innate immune activation via Dectin-1 receptors, which recognize fungal components like beta-glucans and trigger inflammatory cascades without IgE involvement
• Many people experience both allergic and innate immune responses
• Regardless of immune response type, everyone exposed to sufficient mycotoxins will experience direct cellular toxicity

The key insight is that even people without IgE-mediated allergies to mold are still mounting immune responses—just through different pathways. The innate immune system recognizes mold through pattern recognition receptors, triggering inflammation even in "non-allergic" individuals.

Beyond immune responses, mycotoxins are biological warfare agents—evolved over millions of years to kill or harm living organisms. They damage human cells through multiple mechanisms that operate independently of any immune recognition. The mitochondrial dysfunction, oxidative stress, protein synthesis inhibition, and DNA damage caused by mycotoxins occur in all exposed individuals; the genetics and hormones merely determine how quickly these toxins are eliminated and how severely the body responds.

What's Next?

Now that you understand what mycotoxins are, how they enter and can damage your body, and why some people are more vulnerable than others, you're ready for Part II, where I cover:

• How to test for mycotoxin exposure
• The strategic use of mycotoxin binders
• The critical role of mineral balance in recovery
• Practical steps to support your body's healing

Understanding the problem is the first step—in Part II, I explore the solutions.

The information in this article is for educational purposes only and is not intended as medical advice. Please consult with a qualified healthcare provider for diagnosis and treatment of health conditions.

Selected references and further reading