Mold Illness: The Sickness Hiding in Our Walls

Oct 25, 2026 · @Thomas Lee Abshier, ND

I stand on the side of the patient who says, “My house is making me sick.” Illness from water-damaged buildings is real, it is common, and it is routinely missed. Most of the people it strikes can recover, but only after someone takes the building seriously.

The typical patient has spent years moving from one doctor to the next. He is tired in a way sleep does not fix, his thinking is foggy, his joints and muscles ache, his sinuses never clear, and he reacts to foods, fragrances and medicines he once tolerated. His laboratory results come back normal, and he leaves with a label such as chronic fatigue, fibromyalgia, anxiety or depression, or with no label at all.

In September 2026, Health and Human Services Secretary Robert F. Kennedy Jr. convened a roundtable on mold at HHS and described how his own family’s flooded farmhouse sickened his wife and most of his children until the house was torn down. That a cabinet secretary would say this publicly marks a change. Until now, federal health agencies have acknowledged mold’s effects on the lungs while treating the broader, multisystem illness as unproven.

This article explains why mold illness is missed, how our buildings came to grow so much mold, who gets sick and why, how to test both the building and the body, how to repair a home in the order that actually works, and how patients recover. Where the field is unsettled, I say so plainly. The uncertainty concerns the details of diagnosis and treatment, not whether damp buildings make people ill.

Why medicine misses it

Three forces keep mold illness out of view: the shape of the illness, the way medicine handles sensitive people, and money.

The illness does not fit a box. Symptoms span many organ systems at once, the mix differs from patient to patient, and they overlap with Lyme disease and its co-infections, long COVID, chronic fatigue syndrome and psychiatric disorders. A physician who sees only a few such patients rarely sees the pattern, and almost none are trained to look for it. Medical students typically receive a few minutes on water-damaged buildings, if anything.

Medicine is built around the average patient. When most people tolerate an exposure and a minority do not, the system tends to conclude the minority’s reaction is not real. Mold makes this worse, because the patient’s spouse, children or coworkers often feel fine in the same building. The patient is doubted by the very people he relies on, and many begin to doubt themselves. Yet these sensitive people are usually the canaries in the mine. They notice first what is affecting everyone in the building to a lesser degree.

Someone is always liable. Mold grows indoors only where water has gone where it should not. That means a builder, landlord, employer, school district or insurer is usually responsible for the conditions. Dr. Ritchie Shoemaker, who has done more than anyone to establish that damp buildings cause illness, argued in Mold Warriors that this liability is the root of the denial: with so many damp buildings, the potential cost is enormous. It is cheaper to maintain that the illness has not been proven. This is the pattern we have seen with tobacco, asbestos and lead: deny the harm, fund doubt, and resist the research that would settle it.

That pattern is now cracking. Lawsuits against the largest national home builders allege that undersized air conditioning, poorly sealed windows and badly ventilated attics are trapping moisture in new homes. Reported examples include homes in Louisiana measured at 70 to 80 percent indoor humidity, a South Carolina settlement of $16.1 million covering more than 200 homes, and a suit by the Seminole Tribe of Florida over more than 450 homes. The builders respond that many problems come from poor homeowner maintenance and that mold testing is inconsistent. Most such disputes never become public, because purchase contracts typically route them into confidential arbitration.

How our buildings learned to grow mold

Modern buildings grow mold for three reasons, and nearly all of them could have been prevented for a small fraction of what the resulting damage costs.

1. Buildings were sealed. After the 1973 oil embargo, homes were insulated and tightened to save energy. A tight house without deliberate ventilation traps the moisture of cooking, bathing and breathing.
2. Buildings are made of mold food. Standard drywall is gypsum wrapped in paper, and paper feeds mold. So do wood framing, plywood, oriented strand board, ceiling tile and carpet padding once they stay wet. Wood is safe if it dries; mold and rot begin when it stays above roughly 19 percent moisture. Framing often gets rained on during construction and is closed in before it dries, because checking it with a moisture meter and waiting costs schedule time.
3. Mechanical systems are sized for cost, not humidity. An air conditioner removes water only while it runs. An oversized unit cools the house quickly and shuts off, leaving it cool and clammy. An undersized unit cannot keep up in humid weather. Bathroom fans vented into attics and leaky ducts running through hot attics add still more water.

The fixes are cheap. Paperless drywall, faced with fiberglass instead of paper, costs roughly 10 to 15 cents more per square foot, about $500 for a typical basement. Properly sized cooling and dehumidification, sealed ducts and dry framing add little to the price of a home. They are skipped because the builder seldom pays for the mold that appears years later; the family who buys the house does.

None of this is new wisdom. The Roman architect Vitruvius warned that damp winds ruin libraries, and Leviticus 14 gives instructions for a house with a spreading growth on its walls: inspect it, remove the affected stones, scrape the interior, and tear the house down if the growth returns. That remains a fair outline of sound remediation.

Who gets sick, and why

A damp building is a risk factor, not a sentence. Several people can live in the same moldy house while only one becomes seriously ill. Understanding which kind of reaction a person has determines what will help him.

Pattern	What it looks like	What usually helps
Allergy	Congestion, headaches, feeling unwell around mold	Reducing the exposure
Toxic illness	Inability to think, widespread pain, sometimes psychiatric symptoms	Leaving the exposure, then clearing toxins
Colonization	Mold living in the sinuses, gut or lungs, so exposure continues after leaving	Treating the colonization
Sensitization	Severe flares from tiny exposures, reactions to many triggers	Clean environment, calming the mast cells and nervous system

These patterns overlap. Chronic fungal sinusitis, for example, is often mistaken for bacterial infection, and repeated antibiotics then disturb the microbes that were keeping the fungus in check.

Why only some people? Two explanations compete. Dr. Shoemaker links susceptibility to particular HLA-DR immune genes, carried by roughly a quarter of the population, and reports that about a quarter of the occupants of a water-damaged building become ill. Dr. Neil Nathan, who trained with Shoemaker, stopped genetic testing because he found the genotype did not predict how patients responded, and because the label frightened them. His view is that a resilient immune system contains a moldy environment until some other blow, such as a serious infection, surgery or grief, breaks containment. Both agree that patients with the supposedly worst genes still recover.

The cell danger response. The most useful framework I know for this illness is Dr. Robert Naviaux’s cell danger response. When a cell senses threat, its mitochondria shift from producing energy to defending the cell. The cell partly shuts down and signals danger to its neighbors and to the nervous system. In health, the cell then heals and returns to normal once the body signals safety. In chronic illness, cells stay stuck in defense. Naviaux lists fungi and toxins among the triggers, and a damp building delivers both.

This model explains much of what makes mold patients so puzzling:

• Each episode makes the next easier to trigger, which Shoemaker called “sicker, quicker.”
• A cell in survival mode overreacts to small stimuli, so a patient may collapse after an exposure no one else notices.
• The danger signal cells release (extracellular ATP) helps drive mast cell release, which helps explain why so many mold patients come to react to everything.
• The response can outlast its trigger, especially if colonization keeps sounding the alarm, so leaving the building is not always enough.
• An active danger response disrupts sleep and keeps the nervous system in fight-or-flight, so the body never receives the signal that it is safe.
• Supplements meant to boost energy can backfire, because they push mitochondria that have deliberately slowed down while danger is still present.

Most important, the cell danger response is protective, not permanent damage. Once the danger is removed and the body receives enough signals of safety, cells can complete their healing cycle. This is why mold illness, frightening as it is, is so often reversible.

Recognizing mold illness

There is no single reliable laboratory test, so the diagnosis rests mainly on the history. The questions that matter most are when the illness began, where the person was living or working at the time, and how he feels when he is away.

Features that point toward a building:

• Fatigue (especially a disproportionate crash after exertion), brain fog and poor sleep that began after a move, a leak or a renovation
• Marked improvement on vacation, with symptoms returning soon after coming home
• A musty smell, visible growth or a known history of water damage
• Symptoms in many systems at once: headaches, body pain, digestive trouble, food sensitivities, light and sound sensitivity, dark circles under the eyes
• Growing sensitivity to odors, chemicals and medicines
• Out-of-character mood changes: anxiety, irritability, rumination, indecision, withdrawal

Some combinations are unusual outside mold illness: constant thirst with frequent urination (often mistaken for a bladder infection), static shocks, stabbing “ice-pick” pains, night sweats and poor temperature control, numbness that does not follow nerve pathways, a metallic taste, intermittent blurred vision, morning stiffness, word-finding trouble, and symptoms that worsen on rainy days.

The simplest test is to leave. A few days somewhere relatively mold-free often brings noticeable relief. Do not overlook the car, whose air conditioning and cabin filter frequently grow mold, or the workplace. Once the illness is entrenched, however, leaving may bring little relief until treatment begins.

Other conditions must be considered, because many of these symptoms are nonspecific. Babesia and Bartonella, tick-borne infections that travel with Lyme, produce the same waxing and waning picture. A decline that began after COVID infection or vaccination does not exclude a building; the added burden often unmasks a mold problem the person had been tolerating.

Testing the building and the body

Test the building first. It is cheaper, more reliable and more decisive than any test of the body.

The building. Conventional inspections rely on air samples, which capture a few minutes of air from the middle of a room and miss the spores and fragments that settle along its edges. Both Shoemaker and Nathan consider them nearly useless for a sensitive patient. The better tools analyze settled dust for mold DNA:

• ERMI measures 36 mold species; Shoemaker considers a score above 2 elevated.
• HERTSMI-2 scores the five species he found most predictive of illness; above 10 is elevated, and it is the better guide to whether a sick person can safely reoccupy a cleaned building.

A homeowner can collect the dust sample himself, which makes this the most economical first step. Who commissions the test matters. In one suit against a national builder, the homeowner’s assessment found the house uninhabitable, while the builder’s own assessment days earlier had found little. Many licensed inspectors have only a few hours of training, so ask any inspector how many mold-sensitive clients he has served.

The body. Shoemaker documented a cluster of laboratory findings in these patients: low melanocyte-stimulating hormone (MSH), elevated MMP-9, C4a and TGF-beta-1, low vasoactive intestinal peptide (VIP), low antidiuretic hormone with high serum osmolality (which explains the thirst and urination), abnormal leptin, and MARCoNS, a multiply resistant staphylococcus deep in the nasal passages. He also uses a visual contrast sensitivity test, an inexpensive screen for subtle neurologic impairment. These findings show that something real is wrong, but they are not specific to mold; Lyme and Bartonella can produce them too.

Urine mycotoxin testing is the most contested test in the field. The laboratories measure accurately, but no one has established what level predicts disease. Mycotoxins also enter the body through food, and repeated daily samples from one person can vary widely. Practitioners who rely on the test find it clinically useful; Shoemaker rejects it. My counsel: give a urine result weight only when it is roughly ten times the upper limit in a clearly symptomatic person. A mildly elevated result means little, and treating it as a diagnosis is one of the main ways mold is overdiagnosed. Blood tests for mycotoxin antibodies have similar limits.

In short, the diagnosis rests on the history, dust testing of the building, and the person’s response to leaving it. Laboratory results are one piece of the picture, not the verdict.

Repairing a home in the order that works

Most home remediations fail because the repair spreads the problem. A leak is fixed and the moldy section is cut out, but spores, fragments and toxins are dispersed through the house during the work and never cleaned up. Remediation succeeds when it is done in this order:

1. Stop the water. Find the source (roof, plumbing, foundation, crawlspace, condensation on ducts, an air conditioner drain pan) and fix it. Keep indoor humidity between 30 and 50 percent, with dehumidifiers if needed.
2. Separate testing from repair. The person who assesses the building should not be the person paid to fix it.
3. Remove contaminated porous material under containment. Moldy drywall, insulation and padding must be cut out, not sprayed. Seal the area with plastic and keep it under negative air pressure so debris is drawn outside rather than into the rest of the house. This is the step most often skipped.
4. Clean everything. HEPA-vacuum and wipe down walls, ceilings, floors and hard surfaces throughout the house, with HEPA air filtration running. Most hard belongings and many fabrics can be cleaned; carpets, rugs and heavily upholstered furniture often cannot.
5. Clean or replace the HVAC system. Mold in ducts, air handlers and drip pans is broadcast every time the system runs. Replace the car’s cabin air filter as well.
6. Start small. Clean the problem area, the air and the surfaces, then see whether symptoms improve before tearing out more. Larger demolition costs more and carries its own risk of spreading contamination.
7. Retest. A HERTSMI-2 test after cleaning is the most objective sign that a sensitive person can return.

The sensitive person should stay elsewhere during the work and until the retest is back. Air purifiers help some patients, but avoid any that produce ozone, and none will help if the source remains.

Ozone and chlorine dioxide gas. Both are marketed as whole-house mold treatments. Ozone gives only temporary results: it reacts near surfaces without penetrating porous material, and it reacts with plastics, rubber and fragrances to form irritating byproducts. Chlorine dioxide gas reacts more selectively and penetrates deeper; laboratory work, including an EPA study after Hurricane Katrina, found it inactivated common indoor molds on building materials. But killing mold does not remove it. Dead Stachybotrys remains toxic, and fumigation did not reduce airborne endotoxin or beta-glucan. Both gases are dangerous to breathe at treatment concentrations, so the building must be vacated. They belong at the end of a remediation, never in place of one.

Finding a safe place to live. For many patients, a clean home is the single most important step in recovery. Be wary of basements, low-lying flood-prone lots, humid or foggy climates, and any home with past leaks, fresh paint over isolated patches, or a dehumidifier running in the basement. New construction is not automatically safer. Ask directly about water damage, and dust-test before signing a lease or closing a purchase. Porous belongings such as mattresses may need to be left behind.

Treating mold illness

No treatment works while a person continues to live, work or drive in a contaminated environment. Ending the exposure comes first. After that, the order of treatment matters as much as the treatment itself, and gentleness matters more than strength.

The established protocols. Shoemaker’s protocol proceeds in twelve steps: removal from exposure, a bile-acid binder (now usually colesevelam, sold as Welchol, rather than cholestyramine), eradicating nasal MARCoNS, removing gluten when antibodies warrant it, correcting each hormonal and immune abnormality in turn, and finally VIP nasal spray. He reports that about 95 percent of his patients recover to functional health. Its drawbacks are cost (a course of VIP alone can run about $10,000), strict building avoidance, poorly tolerated binders, and few certified practitioners. Nathan instead believes most of his patients are colonized, uses antifungals, chooses binders by toxin, and addresses limbic, vagal and mast cell dysfunction before patients can tolerate treatment. Shoemaker attributes most current cases to bacterial products rather than fungi and opposes antifungals. The two likely see different populations, and some patients fit each approach while others fit neither.

Sequence through the cell danger lens. Depending on the patient, treatment takes one of three orders:

1. Calm the danger response alone, when the trigger is long gone.
2. Remove the active danger (such as colonization), then calm the response.
3. Calm the response, remove the danger, then calm the response again, for patients so reactive that attacking the fungus first causes a severe flare.

Many patients also need a gentle preparatory phase before any detoxification, and improved fluid circulation and lymphatic drainage, so that mobilized toxins actually leave the body rather than settling elsewhere. Too strong a therapy for where the body currently is sets these patients back more often than any other mistake.

Binders or antifungals first? Binders such as colesevelam, cholestyramine, charcoal, clay and chlorella trap toxins excreted in bile so they leave in the stool rather than being reabsorbed. They help some patients greatly and others not at all, and constipation is common. A practical way to choose: begin a very small dose of a gentle antifungal, such as nystatin or undecylenic acid. If the patient flares badly, he needs binders first; if not, he may be spared months of binders that would not have helped.

Colonization. When sinus or gut symptoms persist after leaving the exposure, colonization is likely, and clearing it usually makes the patient far less reactive. Nystatin acts locally but many molds resist it. Among oral antifungals, itraconazole is often preferable to fluconazole, though it carries an FDA boxed warning for heart failure and many drug interactions and must be prescribed by someone experienced with it. For the sinuses, a pulsating irrigator with saline and xylitol, or with baking soda (the best-documented additive for fungal sinus disease), is a sound and economical foundation.

Oxidative therapies. Some patients improve markedly with oxidative therapies. Of these, ozone has by far the most published research, and clinic-administered approaches such as ozone autohemotherapy, and rectal ozone for colonic colonization, have a growing following among practitioners. Hyperbaric oxygen improved attention and reaction time in one small study of mold-exposed patients. Practitioners also report benefit from very dilute hydrogen peroxide or chlorine dioxide by mouth or in sinus rinses. I urge real caution here: these are not benign household remedies, the FDA has warned against drinking chlorine dioxide products, and concentrations that irritate tissue do harm. These belong under the supervision of a physician experienced with them, at low doses, and never as a substitute for removing the exposure.

Supportive care. Sauna (started briefly, and avoided in pregnancy or significant heart disease), an anti-inflammatory diet that removes gluten and mycotoxin-prone foods such as dried fruit and aged cheese, low-dose naltrexone, and phosphatidylcholine all help some patients.

Hypersensitivity. The most reliable cure for sensitization is a clean environment plus clearing any internal colonization. Low-dose immunotherapy sometimes helps after that. Mast cell stabilizers and limbic retraining programs (such as DNRS, the Gupta program or the Safe and Sound Protocol) help a person who is in a clean home yet still reacting to everything. In the cell danger model, these work by supplying the safety signals the body needs to stand down. Deep sleep, time outdoors, friendship and a less stressful life are part of the treatment, not extras. A new pattern takes about three months to settle, so avoiding re-exposure and heavy stress during the first months of recovery is especially important.

Mold and Lyme together. When both are present, treat the mold first. Mold primes the mast cells so strongly that Lyme treatment provokes severe flares; once the mold is cleared, Lyme treatment usually goes far better.

Why the concern stands

The areas of real uncertainty are worth naming. No test for mold illness has been validated against a gold standard. The leading clinicians disagree about whether fungi or bacterial products drive most cases, whether to use antifungals, and whether urine mycotoxin testing means anything. Damp housing often goes with poverty and stress, which could confound some population studies. None of these uncertainties weakens the central claim that water-damaged buildings make susceptible people seriously ill. The reasons for confidence are these.

The respiratory harm is already accepted. The World Health Organization concluded in 2009 that dampness and mold increase respiratory symptoms, allergy and asthma and disturb the immune system. An analysis by researchers at Lawrence Berkeley National Laboratory estimated that about 21 percent of current U.S. asthma cases, some 4.6 million, are attributable to dampness and mold at home. It would be strange if an exposure that inflames the airways stopped at the airways.

The multisystem findings are consistent across countries and study designs. Reported findings include a several-fold rise in nervous-system symptoms and brain fog among employees of a water-damaged hospital; autoimmune disease 8 to 10 times more common among Finnish workers in water-damaged buildings; roughly a third of students and teachers from one damp Finnish school developing autoimmune conditions over 20 years; a 34 to 44 percent higher risk of depression in damp homes across eight European cities; and more than doubled odds of depression among older adults in China. Animal studies show that inhaled Stachybotrys inflames the brain and impairs memory, and some mycotoxins cross the blood-brain barrier.

Patients recover when the exposure ends. The strongest evidence is clinical: people who improve away from a building, relapse on return, and recover once the building is repaired or left. Confounding by poverty does not explain a symptom that lifts on vacation.

The incentives run toward denial. Builders, landlords, insurers and school districts face enormous liability if damp buildings are acknowledged as a cause of chronic illness. Warranty reserves at the largest builders run a few thousand dollars per home, purchase contracts often exclude mold and force confidential arbitration, and the cheapest construction wins on price. When the parties who would pay for the harm also shape what counts as proof, a lack of official recognition tells us little.

It is unnatural to live this way. People did not evolve sealed inside paper-faced walls with recirculated air. Our ancestors, from the Roman builders to the priests of Leviticus, recognized a spreading growth on a wall as a threat to those who lived there. Common sense and the accumulating evidence point the same way.

Recovery

Despite their disagreements, the leading physicians in this field report that most of their patients recover, and many stay well for years, even when they must sleep in hotels and other imperfect buildings. Many who completed limbic and vagal retraining describe themselves as healthier than before they fell ill, which is what the cell danger model predicts once healing is allowed to finish.

That is the message I most want a mold patient to hear. Most homes can be repaired, most belongings can be cleaned, and most people get well. If you suspect your home, the first step is simple and inexpensive: test the dust, and notice how you feel when you are away.

The larger lesson is for the rest of us. Patients sensitive to mold are the canaries of a problem we all share. We have built houses to be fast and cheap and left the families inside them to absorb the cost. Remedies such as paperless drywall, dry framing and properly sized air conditioning cost very little per home. Builders will adopt them when buyers know to demand them, and when the law stops letting the harm be cheaper than the prevention.

Sources and further reading

• A Midwestern Doctor, “Why Mold Illness Goes Unrecognized,” The Forgotten Side of Medicine (Substack), 25 October 2026. The source of most figures, studies and lawsuit details cited here.
• Ritchie Shoemaker, Mold Warriors (2005) and Surviving Mold (2010); practitioner list at survivingmold.com.
• Neil Nathan, Toxic (2018).
• World Health Organization, Guidelines for Indoor Air Quality: Dampness and Mould (2009).
• Mudarri D, Fisk WJ, “Public health and economic impact of dampness and mold,” Indoor Air 17 (2007): 226–235.
• Naviaux RK, “Metabolic features of the cell danger response,” Mitochondrion 16 (2014): 7–17.
• International Society for Environmentally Acquired Illness (ISEAI), directory of physicians and indoor environmental professionals: iseai.org.

Editor’s note: figures in this draft were taken from the source article and have not been checked against the original studies.