What symptoms and health effects can be caused by toxic mould exposure? it goes beyond just allergies!
When moisture becomes an issue indoors, it can lead to an overgrowth of biological contaminants in water-damaged buildings (WDBs). These environments create a “chemical stew” of pollutants that can harm the health of occupants. Like many environmental toxins, mould exposure has a cumulative effect, gradually building up until it surpasses the body’s ability to cope. People’s responses vary widely—some are more susceptible, and symptoms differ greatly. In many cases, mould toxicity symptoms can persist even after someone has left the affected building due to genetic inability to detox biotoxins.
In a healthy indoor environment, the air typically contains fewer fungi than the outdoor air, which has a wider variety of fungal species. In a WDB, however, certain fungi may become more dominant, resulting in a “spectral shift” towards specific species. Various microbial agents contribute to health issues in a WDB, including fragments, mycotoxins, and other toxic substances released by mould, bacteria, and even decaying building materials. Although mould is often the primary focus, numerous microbes, such as bacteria like actinomycetes, contribute to the adverse effects seen in these environments.
A WDB also promotes dust mite growth and can attract pests like cockroaches and rodents, which produce allergens. Surprisingly, some of the worst-affected buildings lack visible mould or musty smells but still cause severe health problems. The range and severity of symptoms vary based on factors like the type of mould present, the individual’s exposure level, and genetic predispositions or allergies.
Mould exposure impacts health in four main ways, which can often overlap:
1. Respiratory and Allergic Effects
2. Infections (and Colonisation)
3. Innate Immune Dysfunction (CIRS)
4. Mycotoxin Toxicity + mVOC’s
1. Respiratory and Allergic Effects
The most widely recognised effect of mould exposure is allergy. Inhaling airborne mould spores can trigger allergies, affecting an estimated 6-10% of the general population and up to 50% of those who are genetically predisposed (atopic). Allergic reactions may cause rhinitis (watery eyes, sneezing, congestion), skin rashes, asthma, and even low blood pressure. Long-term exposure can lead to chronic respiratory issues like rhinosinusitis and hypersensitivity pneumonitis.
Mould can cause these reactions whether it’s alive or dead, so physically removing mould is more important than “killing” it with chemicals. Repeated mould exposure can also sensitise people who were previously unaffected, and worsen the symptoms of those already allergic.
A 2009 World Health Organization review found that mould and dampness in buildings were associated with a 30-50% increase in respiratory and asthma-related conditions. Mould-related irritants can worsen existing asthma, trigger coughing, wheezing, and hay fever, and heighten sensitivity to other inhaled allergens, even in non-allergic individuals.
2. Opportunistic Infections
Living or working in a damp building increases the risk of infections, especially in children. These include respiratory infections like pneumonia, bronchitis, and sinusitis, as well as ear infections. Damp environments can also support fungal growth within the body, leading to infections such as candidiasis and aspergillosis. Mould can also cause skin infections like athlete’s foot and ringworm, particularly in people frequently exposed to mould spores, such as farmers or horticulturalists.
3. Innate Immune Dysfunction (CIRS)
Research using DNA sampling has revealed that about 25% of people are genetically susceptible to Chronic Inflammatory Response Syndrome (CIRS), a severe immune reaction triggered by toxins found in WDBs. Often called “Toxic Mould Illness,” this condition results from biotoxins that persist in the body due to an inability to clear them. Though not well known to the public, there are over 1700 scientific articles on this condition, initially named "Sick Building Syndrome" in the 1970s.
The body's appropriate response to microbes in a WDB is for the immune system to respond by binding the biotoxins for filtration by the liver, kidneys, and other organs to excrete. For those with specific genotypes (primarily polymorphisms of the HLA DR/DQ genes), this binding does not happen, and the biotoxins continue to circulate indefinitely within the body - even after the person has moved away from the mouldy home/office. As the body tries to fight off toxins it cannot remove, prolonged production of immune and inflammatory responses causes symptoms that most would not know to attribute to WDBs and mould exposure. The illness is multi-system and multi-symptom and can include neuropsychiatric effects (depression, anxiety, rage), fatigue, muscle ache and joint pain, brain fog and poor concentration, sudden weight gain/loss, sleep disturbances, gastrointestinal issues, chemical sensitivities - often whilst appearing outwardly healthy. Individuals who fall sick will often become highly sensitive to these biotoxins due to immune system damage and must avoid mould and WDB's to feel well.
Research has revealed that CIRS patients can have 13 different clusters of symptoms. Symptoms in 8 or more clusters (the coloured boxes below) is highly consistent with CIRS. In children, 5 of 13 is significant and warrants further evaluation.
4. Mycotoxins and Microbial VOCs
Microbial Volatile Organic Compounds (mVOCs) are gaseous byproducts released by mould and other microbes, contributing to “musty” odours. These compounds include a mix of alcohols, aldehydes, esters, and other chemicals that can cause symptoms like eye irritation, headaches, dizziness, and fatigue. Testing for mVOCs is complex, as similar compounds are also released by materials like furniture and fragrances, complicating the identification of sources in WDBs.
Certain moulds also produce mycotoxins, toxic chemicals that act as a defence mechanism against other organisms. These toxins are incredibly small (around 0.1 microns) and can enter the body through inhalation, ingestion, or skin contact. Once in the body, mycotoxins can cause oxidative stress and disrupt cellular function, leading to neurological, cardiovascular, gastrointestinal, and immune problems. For example, aflatoxin B1, a known carcinogen, is linked to liver cancer upon ingestion and lung cancer upon inhalation. Mycotoxins affect about 25% of the world’s crops annually, with contamination found in grains, nuts, and other foods.
Even in the absence of immediate symptoms, mycotoxins and mould exposure can silently impact health over time. Integrative medicine practitioners trained in mould toxicity can assess patients’ exposure using blood, urine, and neuro-imaging tests. While many effects of mould exposure are well-documented, research continues to reveal more about the complex interactions between indoor mould and health.