10 Warning Signs of Mould Toxicity

warning signs of mould toxicity


In this post, I discuss the 10 Warning Signs of Mould Toxicity, looking at warning signs, symptoms, and what can be done.

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10 Warning Signs of Mould Toxicity

  1. Multiple chemical sensitivity.
  2. Chronic fatigue. 
  3. Brain fog and poor cognition.
  4. Respiratory issues such as shortness of breath.
  5. Gut issues, including SIBO and constipation.
  6. Skin issues.
  7. Chronic sinus issues.
  8. Changes in vision – blurry vision or eye irritation.
  9. Neurological symptoms – numbness, tingling, nerve pain.
  10. Feeling better when out of the home.


Multiple Chemical Sensitivity

“Multiple chemical sensitivity frequently develops after being exposed to a mouldy water damaged property and can have a severe impact on a person’s life” (source).

Multiple Chemical Sensitivity, according to some researchers, is a “controversial disorder” in which patients “claim” to become ill from environmental exposure to low levels of various environmental toxins. This could be petroleum-based but could be unrelated chemicals, including cleaning products, detergents, plastics, carpets, pesticides, and some synthetic and natural fragrances. 

Even the writing in the *medical research* (!) shows us how people question the validity of this condition, describing it as “controversial” and stating that patients “claim” their symptoms started a certain way. While I have not had an official diagnosis of this condition, I have been extremely reactive to my environment and had sneezing fits walking past someone with a strong perfume or walking down certain isles of the supermarket. I get what it’s like! It is very, very rare I ever experience this anymore, so I want you to know that there is hope – but it is likely going to be a slow process.

What we do know is that symptoms can arise gradually over time or immediately following a single high-level exposure.

There are numerous symptoms that may be associated with multiple bodily systems and include: perceived hypersensitivity to the smell of chemicals, nausea, dyspepsia, fatigue, dizziness, headache, upper respiratory discomfort, runny eyes, chest and throat pain, arthralgia, brain fog, and other cognitive and memory problems, and mood changes such as depression or anxiety (source).

Removal from the environment of the offending agents frequently mitigates the experienced symptoms (source). However, this is, of course, not a sustainable long-term strategy and the root cause of the sensitivity must be explored. One possible explanation is mould exposure.

Chronic Fatigue

One of the most common warning signs of mould toxicity is chronic fatigue syndrome. I have seen this association in my clinic a lot over the last decade. 

One study (source) investigated whether mycotoxins could be identified in the urine from patients suffering from chronic fatigue syndrome. Urine was tested for aflatoxins, ochratoxin A, and trichothecenes. 

93% were positive for at least one mycotoxin, and just under 30% of the patients had more than one mycotoxin detected in their urine. 

Ochratoxin A was the most prevalent (83%), and trichothecenes was the next most common, being detected in 44% of patients. 

The patients were asked about their known exposure to water-damaged buildings, and histories indicated current and/or past exposure in over 90% of patients. The researchers then performed some environmental testing in some of the water-damaged buildings these patients lived in. This testing revealed the presence of potential mycotoxin-producing mould species and mycotoxins in the environment of the water-damaged buildings. 

Interestingly, the researchers performed some testing on a healthy population, acting as a control, who had no known history of exposure to water-damaged buildings or mouldy environments. It was, of course, the same laboratory that was used to test these healthy individuals; the lab, of course, used the same methods. What they found was that there were no positive cases. (source)

In another study, the researchers investigated the rates of Aspergillus-derived toxin levels, Aflatoxin, Ochratoxin A, and Gliotoxin, in the urine of 236 chronic fatigue syndrome patients with a history of chronic exposure to mould. 

Again, in over 90% of patients, evidence was found of exposure to mould, with Ochratoxin A being the most prevalent mycotoxin. 

In conclusion, this study provides preliminary epidemiological evidence that a potential cause of chronic fatigue syndrome is exposure to mycotoxins from a water-damaged building.

The authors, based on the findings from this study, proposed that the results should be taken into consideration for future control studies (source).

Brain fog and poor cognition

Several studies have indicated that indoor mould exposure can alter brain blood flow, autonomic nerve function, and brain waves and worsen concentration, attention, balance, and memory. (source)

There are various ways that mycotoxins cause sickness, read my blog How Mould Makes You Sick, but one that is relevant to brain fog and poor cognition is related to inflammation and the production of pro-inflammatory cytokines, especially from mast cells. (source)

In one study, neuropsychological data and symptoms were evaluated from 31 individuals that had been exposed to toxic mould from water-damaged buildings. The researchers found that the majority of individuals were found to have impaired cognitive functioning. Memory and executive function were the two most commonly affected. 

This study adds to a growing body of literature associating exposure to mycotoxins to cognitive dysfunction (sources). If you are unaware of Dr. Bredesen’s work, I’d recommend checking it out, especially on inhalational Alzheimer’s.

Respiratory issues such as shortness of breath

When it comes to warning signs of mould toxicity, the most comprehensive evidence is associated with respiratory issues. In fact, there is so much research here I could write a big blog post just on this. Here are three examples from countless:

  1. In one study, it was found that asthma was common among subjects exposed to reported visible mould (32%) and reported mouldy odour (42%). It was concluded that exposure to visible mould and mouldy odour were risk factors for asthma (source).
  2. In another study, it was concluded that home environments with visible mould and mould spore exposure increase the risk of allergic respiratory health outcomes in children. (source). This was a systematic review of the evidence to date.
  3. And finally, in another study, the researchers concluded that a mouldy home environment in early life is associated with an increased risk of asthma, particularly in young children, as well as symptoms associated with allergic rhinitis in school-age children. (source)

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Gut issues, including SIBO and constipation.

Mycotoxins can alter the normal intestinal functions such as barrier function and nutrient absorption. Some mycotoxins also affect the histomorphology [structure] of the intestine. (source)

I got in to mould because I was starting to see so many clients not respond to conventional gut healing protocols. We were forced to look elsewhere and it quickly became apparent that mould causes chronic gut issues. So warning signs of mould toxicity absolutely include  gut issues, and in particular gut issues that aren’t healed through the typical interventions – diets, pro- and prebiotics among others.

There is a bi-directional relationship between mycotoxins and the gut microbiome. 

On the one hand, it has been shown that the gut microbiome is capable of eliminating mycotoxins from the body naturally, provided that the person is healthy with a balanced gut microbiome. 

On the other hand, mycotoxins have been shown to negatively affect the composition of the gut microbiome. 

“Most, if not all, of the reported effects of mycotoxins on gut health are negative” – what we see is clear – a reduction in the more beneficial “commensal” bacteria accompanied by an increase in gut pathogens (more problematic bacteria/fungi/parasites). (source)

Interestingly, in some research, it has been shown that the severity of hepatocellular carcinoma (the most common type of liver cancer) can be positively influenced by supporting a healthy gut microbiome via probiotic supplementation.

Probiotics, which generally help restore the natural harmony of gut microbiota coupled with its mycotoxins reducing ability, could increase its health-promoting value. (source)

The authors did conclude that more studies are needed to understand the interaction between the gut microbiome and mycotoxins, but it is certainly a very positive area of research, and if suffering from mould illness, supporting the gut is an essential aspect of recovery. 

Skin issues

T-2 toxin has toxicological effects on human and animal digestive, immune, nervous, and reproductive systems. In addition, the most significant toxic effect can be observed on the skin. (source)

T-2 toxin is the most toxic fungal secondary metabolite produced by different Fusarium species (source)

It has been shown that T-2 toxin has a strong skin irritation effect and can be absorbed even through intact skin – as discussed in my blog How Mould Makes You Sick. Toxic effects can include redness, blistering, and necrosis. 

While understanding the exact mechanisms causing this damage, the results of an in vitro human skin fibroblast model revealed that the T-2 toxin induces necrosis as a toxicity effect. (source)

Chronic sinusitis/rhinosinusitis

The sinuses are the most likely candidate as a site for the internal mould and mycotoxin production (source).

There is also good evidence showing us that a significant number of those suffering with chronic fatigue syndrome have been exposed to toxic mould from water-damaged buildings and have been colonised by mould in the sinuses. How do we know this?

Well, over 90% of the patients in the study gave a history of exposure to a water-damaged building, mould, or both. What’s important to know, though, is that exposure histories often indicated the water-damaged building/mould exposure occurred many years prior to the mycotoxin testing. Many of these patients have not had recent or current exposure to a water-damaged building or mouldy environment. 

Despite this, these patients had chronic symptoms and the presence of significantly elevated concentrations of mycotoxins in their urine. 

The persistence of mycotoxins suggests that there may be an internal source of mould that represents a reservoir for ongoing mould toxins that are excreted in the urine. Otherwise, one would anticipate that the toxins would have cleared over time. 

The authors theorised that the mould is harboured in biofilm communities and generates “internal” mycotoxins, partly explaining why it can sometimes be hard to successfully treat. (source)

The good news is that studies have demonstrated success with treating patients with ‘intranasal amphotericin B’. This was shown in both chronic rhinosinusitis patients, as well as those with chronic illness following mould exposure. Studies have also shown that Amphotericin B has superior activity in biofilm models as opposed to other antifungals (source)

Changes in vision – blurry vision or eye irritation.

Exposure to moulds and mycotoxins not only contributes to the onset of respiratory disease but also affects the ocular surface. (source)

Low but persistent inflammation, caused by environmental factors, such as fungal toxins, leads to irritation and sensitisation and could be responsible for allergic manifestations, which, in turn, could lead to mucosal hyper-reactivity. 

As the ocular allergy symptoms are almost always combined with rhinitis, and as nasal and ocular mucosa belong to a complex mucosal and lymphoid tissue network, it would be of interest in future work to study the relation between the ocular surface and nasal mucosa in the development of the inflammatory reaction. (source)

The visual contrast test, which can be performed online, is a measure of one of the neurologic functions of vision known as “contrast.” It is known through the work of Dr. Richie Shoemaker that biotoxins (such as mycotoxins) impair the ability to detect subtle contrast within 24-36 hours after exposure.

As discussed in my blog, CIRS Symptoms: Chronic Inflammatory Response Syndrome, The visual contrast test has a 92% accuracy rate. This is based on years of data collected from tens of thousands of patients since Dr. Shoemaker began using it.

Neurological symptoms – numbness, tingling, nerve pain.

Human exposure to moulds, mycotoxins, and water-damaged buildings can cause neurologic and neuropsychiatric signs and symptoms. Many of these clinical features can partly mimic or be similar to classic neurologic disorders, including pain syndromes, movement disorders, delirium, dementia, and disorders of balance and coordination (source)

In a recent study of mould-exposed patients, the participants were treated with intranasal amphotericin B with or without systemic antifungals. The patients were monitored before and after treatment. 90% of the patients had a dramatic decrease in their systemic symptoms, including neurological conditions of tremor, ataxia, and vertigo, among others. (source)

Feeling better when out of the home.

Leaving this one till last! When it comes to warning signs of mould toxicity, this is an obvious one…..if you notice your symptoms improve when out of the house, . How do you feel when you go away for a weekend? Or on holiday? While it could be stress is a key factor driving symptoms, it is also possible you are being exposed to mycotoxins (or some other environmental irritant). 


It is clear that there are numerous warning signs of mould toxicity – and we haven’t even touched on warning signs from a building perspective! We need to consider whether there have been any historical water leaks damp issues such as rising damp. Is there a lot of condensation in the property?

I always recommend buying a hygrometer as a way of monitoring humidity – ideally, we need to keep humidity under 50% to avoid risk of mould growth. A dehumidifier may be needed to help manage this – we were shocked when we realised the humidity in our kitchen gets up to 75% when cooking (although perhaps this shouldn’t have been too surprising). But it was always well above 50%, and so we have a dehumidifier in there now. It pulls 24 litres of water out of the air per day!

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