Is Mould Making You Ill? A Functional Medicine Practitioner’s Guide to Mould Toxicity Symptoms

What if the answer is in your walls?

As a Functional Medicine practitioner, I see this scenario regularly. In a country like the UK — where damp, poorly ventilated housing is widespread — mould exposure is one of the most common, and most under recognised, root causes of chronic illness I encounter.

This guide is for anyone who suspects their home might be affecting their health, or who has been searching for answers that conventional medicine hasn’t provided. It draws on peer-reviewed research as well as my own clinical experience, and approaches the topic through the lens of root cause health and longevity optimisation — not just symptom management.

What Is Mould Toxicity — And Why Is It So Misunderstood?

Mould toxicity refers to the health effects caused by exposure to mould and the toxic compounds it produces, called mycotoxins. It is distinct from a mould allergy — which is what most people, and most conventional doctors, think of when mould and health are discussed in the same breath.

Research has identified four mechanisms through which mould exposure can affect human health:

1. Allergy — an allergic reaction to mould spores, similar to hayfever
2. Infection — mould establishing itself in the body, particularly in the sinuses and lungs
3. Inflammation — a persistent innate immune response affecting the entire body
4. Toxicity — the direct effects of mycotoxins penetrating tissues, organs, and the brain

A landmark 2021 study found that mould inhalation triggers the same immune pathways as bacterial or viral infection, activating brain-resident immune cells called microglia, and producing cytokine-driven inflammation that causes fatigue, pain, anxiety, and cognitive impairment — even from non-toxic mould spores. Neurologists in multiple studies have noted that the cognitive and neurological profiles of mould-exposed individuals are indistinguishable from those of people with mild to moderate traumatic brain injury.

This is not a minor or fringe concern. It is a well-documented, multi-system problem — and one that conventional medicine, focused primarily on acute allergic responses and severe invasive infections, is largely not trained to detect.

References:

• Harding CF et al. Mold inhalation causes innate immune activation, neural, cognitive and emotional dysfunction. Brain Behav Immun. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC7231651/
• Shoemaker RC et al. A Review of the Mechanism of Injury and Treatment Approaches for Illness Resulting from Exposure to Water-Damaged Buildings. ScientificWorldJournal. 2013. https://pmc.ncbi.nlm.nih.gov/articles/PMC3654247/

Mould Toxicity Symptoms: Why They Are So Hard to Pin Down

One of the reasons mould toxicity is so frequently missed is that its symptoms are vague, wide-ranging, and easy to attribute to other causes. From a root cause health perspective, this is precisely why a thorough, investigative approach matters.

Some of the most common mould toxicity symptoms I see in clinical practice include:

• Anxiety and depression
• Brain fog, poor concentration and memory problems
• Unexplained fatigue that doesn’t improve with rest
• Body aches and slow recovery from exercise
• Arthritis and joint pain
• Tremors
• Migraines and headaches
• Digestive problems — diarrhoea, bloating, food intolerances
• Hayfever and asthma (especially year-round, not just seasonal)
• Sleep apnoea and disrupted sleep
• Histamine intolerance and mast cell activation syndrome (MCAS)
• A lowered immune system and frequent infections
• Hormone imbalances linked to conditions such as endometriosis, fibroids, PMDD
• Autoimmune conditions such as Hashimoto’s thyroiditis and Multiple Sclerosis
• ADHD and autism spectrum disorder

It is a long and varied list — and that’s precisely the point. Mycotoxins are odourless, invisible, and tasteless. They create systemic inflammation and disruption that manifests differently in each person. Research has shown that mycotoxin nanoparticles in indoor air can be 1,000 times more numerous than the actual mould spores that produce them — meaning you can be significantly exposed even with small amounts of mould present (and often hidden behind wallpapers!).

A useful clinical clue: do your symptoms improve when you are away from home for a few days? If so, your indoor environment may warrantsinvestigation.

References:

• Crago BR et al. Mold and Mycotoxin Exposure and Brain Disorders. J Integr Neurosci. 2023. https://www.imrpress.com/journal/JIN/22/6/10.31083/j.jin2206137
• Janssen S et al. Mold, Mycotoxins and a Dysregulated Immune System. Int J Mol Sci. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8619365/
• Ratnaseelan AM et al. Effects of Mycotoxins on Neuropsychiatric Symptoms and Immune Processes. Clin Ther. 2018. https://pubmed.ncbi.nlm.nih.gov/29880330/

What Mycotoxins Actually Do to the Body

Once inhaled or ingested, mycotoxins can travel through the bloodstream into virtually every part of the body — including the brain. Their size (approximately 0.1 microns, similar to a virus) allows them to penetrate deep into lung tissue, cross the blood-brain barrier, and even travel directly to the brain via olfactory pathways in the nose.

Inside the body, they trigger chronic inflammation and oxidative stress — essentially, cellular damage. This includes damage to brain cells, gut cells, and the mitochondria (our cellular energy producers), as well as disruption to RNA and DNA biosynthesis.

Specifically, research has shown mycotoxins can:

• Compromise the blood-brain barrier and damage the gut lining, contributing to ‘leaky brain’ and ‘leaky gut’
• Deplete glutathione — the body’s master antioxidant — impairing the immune system’s ability to clear toxins, cellular damage, and to protect the brain
• Activate mast cells, triggering histamine release and potentially contributing to MCAS
• Disrupt mitochondrial function, contributing to the profound fatigue commonly reported by sufferers
• Cause myelin damage — a feature also seen in conditions such as Multiple Sclerosis. Studies have found that mycotoxin-exposed individuals can develop antibodies to their own nerve tissue, including myelin basic protein
• Deplete dopamine-producing neurons — research in mice found that even just the volatile compound responsible for mould’s musty odour caused significant loss of dopamine neurons and Parkinson’s-like symptoms
• Increase amyloid-beta plaque formation — mycotoxin-triggered neuroinflammation has been linked to deposition of amyloid plaques, a hallmark of Alzheimer’s disease

Perhaps most concerning from a longevity and prevention perspective: mould exposure has been shown to (sometimes long-term) rewire immune responses in susceptible individuals. A 2021 study found that chronic exposure to mouldy environments changed how immune cells responded to future mould or mycotoxin exposure — with significantly different cytokine patterns compared to unexposed controls. This immune reprogramming can persist even after the environmental exposure has stopped, making it harder for the body to return to a balanced, healthy state.

References:

• Crago BR et al. Mold and Mycotoxin Exposure and Brain Disorders. J Integr Neurosci. 2023. https://www.imrpress.com/journal/JIN/22/6/10.31083/j.jin2206137
• Janssen S et al. Mold, Mycotoxins and a Dysregulated Immune System. Int J Mol Sci. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8619365/
• Shoemaker RC et al. A Review of the Mechanism of Injury and Treatment Approaches for Illness Resulting from Exposure to Water-Damaged Buildings. ScientificWorldJournal. 2013. https://pmc.ncbi.nlm.nih.gov/articles/PMC3654247/
• Harding CF et al. Mold inhalation causes innate immune activation, neural, cognitive and emotional dysfunction. Brain Behav Immun. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC7231651/
• Metabolic disruption by mycotoxins: focus on metabolic endpoints steatosis, adipogenesis and glucose metabolism. PMC. 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC12085319/

Who Is Most Vulnerable?

Not everyone exposed to mould will become significantly ill — which is part of why the problem remains so misunderstood. Key vulnerability factors include:

Genetics: Research suggests approximately 25% of people carry gene variants (in the major histocompatibility complex) that make them susceptible to long-term inflammation following mould exposure, including changes in brain structure and function, and initiation of autoimmune problems.

Glutathione gene variants: Individuals with genetic mutations affecting glutathione pathways — which govern the body’s primary antioxidant defence — have a reduced ability to neutralise mycotoxin damage, increasing their risk significantly.

Pre-existing immune dysregulation: Those with autoimmune conditions or other immune system challenges are at higher risk of a more severe and prolonged response.

Children: Particularly concerning from a prevention and longevity standpoint is the evidence around children. A controlled study measuring IQ in children exposed to indoor mould for more than two years found a statistically significant deficit of approximately 10 IQ points, with longer exposure tripling the risk of low IQ scores. Neurophysiological testing has also revealed abnormalities in brainstem, somatosensory, and visual evoked potentials in children with long-term mould exposure.

In short: the same mouldy home can leave one person unaffected and another seriously unwell. This does not mean the second person is imagining it.

References:

• Harding CF et al. Mold inhalation causes innate immune activation, neural, cognitive and emotional dysfunction. Brain Behav Immun. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC7231651/
• Janssen S et al. Mold, Mycotoxins and a Dysregulated Immune System. Int J Mol Sci. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8619365/
• Shoemaker RC et al. A Review of the Mechanism of Injury and Treatment Approaches for Illness Resulting from Exposure to Water-Damaged Buildings. ScientificWorldJournal. 2013. https://pmc.ncbi.nlm.nih.gov/articles/PMC3654247/
• Crago BR et al. Mold and Mycotoxin Exposure and Brain Disorders. J Integr Neurosci. 2023. https://www.imrpress.com/journal/JIN/22/6/10.31083/j.jin2206137

Can Mould Affect Mental Health?

Absolutely.

The mechanisms are increasingly well understood. Mycotoxin-triggered brain inflammation can disrupt the metabolism of tryptophan — diverting it away from serotonin production and towards the kynurenine pathway, which generates inflammatory mediators. The result: decreased serotonin availability alongside increased glutamate (an excitatory neurotransmitter that in excess becomes neurotoxic), nitric oxide, and other inflammatory compounds. Research has identified this as a likely driver of the psychological disturbances, depression, and anxiety seen in mould-exposed individuals.

Dopamine is also affected. Ochratoxin A — one of the most common mycotoxins found in water-damaged buildings — causes loss of dopaminergic neurons in the substantia nigra and striatum: the same regions affected in Parkinson’s disease. In combination with excess glutamate, reduced dopamine produces a picture that closely mirrors ADHD: difficulties with focus, motivation, impulse control, and hyperactivity.

Mould can also stimulate mast cells to release histamine in the brain, contributing to neurological overexcitability and symptoms including panic attacks, rumination, migraines, and anxiety.

And the link to autism spectrum disorder is increasingly evidenced: multiple studies have found significantly higher levels of mycotoxin antibodies in children with ASD compared to controls, with researchers at Tufts University School of Medicine concluding that mycotoxin exposure can directly affect the nervous system and contribute to neurodevelopmental disorders.

References:

• Ratnaseelan AM et al. Effects of Mycotoxins on Neuropsychiatric Symptoms and Immune Processes. Clin Ther. 2018. https://pubmed.ncbi.nlm.nih.gov/29880330/
• Janssen S et al. Mold, Mycotoxins and a Dysregulated Immune System. Int J Mol Sci. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8619365/
• Crago BR et al. Mold and Mycotoxin Exposure and Brain Disorders. J Integr Neurosci. 2023. https://www.imrpress.com/journal/JIN/22/6/10.31083/j.jin2206137

The Fish Bowl Problem — Why Environmental Testing Matters

I often use this analogy with clients: if the water in a fish bowl is polluted, the fish will get sick. No matter how many supplements or treatments you give that fish, unless the water is cleaned, it will stay ill.

The same principle applies here. From a root cause health standpoint, any strategy to clear mycotoxins from the body will only be effective if the environmental exposure has first been removed. This is why home mould testing is not an optional add-on — I believe it to be the essential first step.

Crucially, you do not need to see visible mould to have a problem. Mould can hide behind wallpapers, and mycotoxin nanoparticles are invisible to the naked eye. A high-quality environmental test — such as the Untold Mould kit (code MIRTHE10 for 10% off!) which uses gold-standard testing technology — can detect what you can’t see.

It is also worth noting that common remediation methods — bleach, UV light, ozone, steam — have been shown in research to be largely ineffective at removing mycotoxins from building materials. Dead mould still produces toxic fragments. Proper remediation requires specialist knowledge, and individuals who have become ill often remain sensitive to the original environment even after it has been treated, unless done thoroughly.

References:

• Shoemaker RC et al. A Review of the Mechanism of Injury and Treatment Approaches for Illness Resulting from Exposure to Water-Damaged Buildings. ScientificWorldJournal. 2013. https://pmc.ncbi.nlm.nih.gov/articles/PMC3654247/
• Crago BR et al. Mold and Mycotoxin Exposure and Brain Disorders. J Integr Neurosci. 2023. https://www.imrpress.com/journal/JIN/22/6/10.31083/j.jin2206137

Can You Recover? A Note on Longevity and Prevention

Yes — and this is what makes early intervention so important from a health optimisation and longevity standpoint.

Recovery is absolutely possible. The body is remarkably resilient when given the right support. Research confirms improvement with comprehensive treatment approaches. However, I won’t sugarcoat it: recovery can take time, particularly when exposure has been prolonged, or where the immune system has been significantly rewired.

The real message here is prevention. We know that mould exposure can contribute to the development of chronic inflammation, which is one of the underlying factors contributing to most ill health conditions — neurodegeneration, autoimmunity, cardiovascular disease, cancer, etc etc— that can manifest years or decades later. The earlier someone identifies and removes their exposure, the better their long-term health trajectory.

From a longevity medicine perspective, the goal is not simply to treat illness after it develops — it is to identify and remove the environmental and biological triggers that erode health over time. Mould is one of the most potent and mostly under recognised trigger.

References:

• Harding CF et al. Mold inhalation causes innate immune activation, neural, cognitive and emotional dysfunction. Brain Behav Immun. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC7231651/
• Shoemaker RC et al. A Review of the Mechanism of Injury and Treatment Approaches for Illness Resulting from Exposure to Water-Damaged Buildings. ScientificWorldJournal. 2013. https://pmc.ncbi.nlm.nih.gov/articles/PMC3654247/
• Janssen S et al. Mold, Mycotoxins and a Dysregulated Immune System. Int J Mol Sci. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8619365/

A Lab Testing-Based Approach: Test, Don’t Guess

This is my clinical motto — and it is particularly relevant here. Most people who come to me have already tried numerous supplements, elimination diets, and protocols. They are exhausted and frustrated. What they need is precision, personalisation, and a full 360 approach.

Mould rewires the immune system, but also the gut microbiome, and with it often leads other knock-on effects, such as hidden food intolerances and allergies, or allowing other infections such as viral, fungal or bacterial to take over, contributing to inflammation, and keeping the person in the loop of ill health. In addition, nutrient or hormone imbalances, or heavy metals, can worsen things, lower resilience, and make it that much harder for the body to rid itself of mycotoxins and. heal. Hence to be effective, one needs to look at the entire root cause/ health puzzle, not only mould in itself. 

A comprehensive, lab testing-based approach to mould toxicity assessment may include:

• Mycotoxin testing (urine or serum antibodies) to identify specific toxin exposure and body burden
• Mould spore testing (urine)
• Environmental testing of the home or workplace
• Gut microbiome analysis — mycotoxins are known to reshape gut microbiota and cause dysbiosis, which in turn affects immune function and toxin metabolism
• Hidden food intolerances and allergies – mould has been shown to induce direct hypersensitive reactions and have immunomodulatory properties (R)   
• Glutathione and oxidative stress markers — given the central role of glutathione depletion in mycotoxin illness
• Nutrient panels — vitamin D, omega-3, and other key immune-support nutrients
• Hormone panels — mould’s immune-suppressing effects frequently contribute to hormonal disruption
• Genetic testing — to identify HLA gene variants, glutathione pathway mutations, and other factors affecting individual susceptibility
• Heavy metal testing — as heavy metals have been shown to strengthen mould biofilm, increasing persistence in the body

This multi-layered, evidence-based picture allows for a truly bespoke treatment protocol — rather than a one-size-fits-all approach that may address some issues while missing others entirely.

References:

• Shoemaker RC et al. A Review of the Mechanism of Injury and Treatment Approaches for Illness Resulting from Exposure to Water-Damaged Buildings. ScientificWorldJournal. 2013. https://pmc.ncbi.nlm.nih.gov/articles/PMC3654247/
• Crago BR et al. Mold and Mycotoxin Exposure and Brain Disorders. J Integr Neurosci. 2023. https://www.imrpress.com/journal/JIN/22/6/10.31083/j.jin2206137
• Janssen S et al. Mold, Mycotoxins and a Dysregulated Immune System. Int J Mol Sci. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8619365/
• Metabolic disruption by mycotoxins: focus on metabolic endpoints steatosis, adipogenesis and glucose metabolism. PMC. 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC12085319/

Where to Start If You Suspect Mould Toxicity

Here is a practical roadmap:

1. See your GP. Always ensure nothing urgent has been missed. Functional Medicine works alongside — not instead of — standard medical care. This is the single most important first step.
2. Test your home. Use a reliable at-home environmental kit such as Untold Mould to rule out — or confirm — ongoing exposure.
3. Seek specialist Functional Medicine support. If your GP gives you the all-clear of anything more sinister, but symptoms persist, work with a practitioner who specialises in mould toxicity and can design a comprehensive, lab testing-based protocol for your individual needs.

Mould toxicity is complex — but it is treatable. The sooner someone connects their symptoms to their environment, the sooner they can begin to reclaim their health and optimise their long-term wellbeing.

Mirthe Eckl is a Functional Medicine practitioner registered with the HCPC, specialising root cause health and longevity optimisation. To find out more or to book a consultation, visit www.mprecisionhealth.com

This article is for educational purposes and does not constitute medical advice. Always consult a qualified healthcare professional regarding your individual health concerns.