Mold Exposure Symptoms: Toxicity, Symptoms, & Testing​

By Charlie Huntington, M.A., Ph.D. Candidate
​Reviewed by Tchiki Davis, M.A., Ph.D.
Being around mold in your home or workplace can lead, over time, to the development of mold exposure symptoms. What are these symptoms, and how can you test for them?​
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One of the weekly tasks in my housing co-op is to clean our fridges. This means wiping down surfaces, checking expiration dates, and composting foods that have gone bad. It is one of my favorite chores, and in my time, I have seen some pretty impressive collections of mold. While I certainly won’t eat the moldy foods, they don’t especially bother me. However, specialty stinky cheeses aside, most foods seem to immediately become 
disgusting to us when mold appears, which is probably a useful survival mechanism on our parts.​

While mold on food is obvious, mold in our living spaces may not be as self-evident. When mold emerges in places that we cannot see or reach as well, it may grow unchecked and without our awareness. Over time, this may come to affect our health, although we may have a hard time identifying why we are experiencing health issues. Let’s look at the science of mold exposure and the symptoms it involves, so that you may be better empowered to ensure that mold is not causing you problems.​
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What is Mold? (A Definition)​

Let’s start by defining mold, as there are many other things in our environments that can impact our well-being. Mold is a term widely used to describe the visible fungi that can appear in indoor environments (Hurrass et al., 2017) – typically buildings such as homes. Mold is a natural phenomenon that occurs when there is enough moisture in an environment for a long enough time. This makes it more likely to develop in areas that are very humid, as well as in places where there is little ventilation, but it can grow on most any surface and in a wide temperature range, provided there is enough moisture in the air or on the surface (Heseltine & Rosen, 2009). Buildings with structural deficiencies are even more likely to develop mold, as water damage, standing water, and leaks can lead to prolonged exposure to moisture on key surfaces.​

Mold develops and reproduces itself in an environment through emitting spores (Hurrass et al., 2017), or tiny biological particles, similar to the seeds that plants give off but typically much smaller. Fungi often release spores into the air, but spores may also be transmitted by animals, such as insects, that come into contact with the fungi. Mold spores are resilient and can survive dry conditions, but in wetter conditions, mold spores are especially likely to develop and spread (Hurrass et al., 2017).

What Are Mold Exposure Symptoms? (A Definition)​

When our bodies come into contact with mold itself, or more often its spores, it physically affects us. While there is a wide range of bodily responses, all humans will experience health consequences, such as compromised immune system functioning, neurological changes, and difficulties with respiration, if exposed to enough mold (Pizzorno & Shippy, 2016). These and other symptoms comprise what we call mold exposure symptoms – they are signals that a person may be experiencing health-impairing exposure to mold in their living or working environments.

Examples of Mold Exposure Symptoms

Mold exposure symptoms involve a range of neurological, respiratory, immune system, and physical behavior symptoms (Pizzorno & Shippy, 2016). Among the neurological symptoms are difficulty concentrating, memory problems, dizziness and lightheadedness, and feeling excessively tired. Respiratory symptoms usually involve irritation in the nose or throat, coughing, or difficulty breathing. Immune system symptoms may manifest as increased susceptibility to getting sick. And finally, people who are experiencing mold exposure may be more likely to slur their speech, have watery eyes, and have difficulty coordinating their bodily movements.

Most Common Mold Exposure Symptoms

Scientists have worked hard to understand which symptoms are most common. For example, in one study that compared people with mold exposure to those without, about 80% of people exposed to mold had neurological and respiratory symptoms, 60% of them were experiencing “brain fog” (a neurological symptom), and about half were experiencing bodily pain related to mold (Hyvonen et al., 2020). While respiratory symptoms are more likely and more severe among people with conditions that put them at risk of breathing issues, such as asthma, they are still common in people with mold exposure (Gent et al., 2002).

Mold Exposure Symptoms & The Nervous System

Some scientists describe mold exposure as neurotoxic, meaning that it is harmful to our nervous systems (Kuhn & Ghannoum, 2003). It is thought that the physical nature of these spores allows them to pass through the blood-brain barrier and enter directly into our nervous system in this way (Campbell et al., 2004).

This can influence our bodies in many ways (Curtis et al., 2004). Less debilitating symptoms might include tingling or numbness in the body, stiffness in joints, or being more sensitive than usual to touch. More impairing (and also much less common) symptoms include seizures and the more general breakdown of the nervous system. And many people with mold exposure will experience memory loss and mental health challenges such as anxiety or depression.

Mold Exposure Symptoms Test Kit

There are a number of ways to test our bodies for mold exposure, as exposure to spores leaves traces in our bodies. A common way to test for levels of mold exposure in our bodies is through analysis of urine samples (Croft et al., 2002), and many testing kits are available for purchase. One example is the MycoTOX Profile, a simple testing kit that involves providing a urine sample that will be analyzed to find out the levels of many different mycotoxins (naturally occurring compounds generated by fungi that are harmful to humans) in your body. This test is available here.

Another kind of test aims to understand whether a person may have a mold allergy (Liang et al., 2006). These testing procedures may include exposing a person’s skin to tiny amounts of certain kinds of mold and watching for a small-scale allergic reaction. Alternatively, blood tests may help determine whether a person is allergic to different molds.

If you would like more information about how to test for mold toxicity, you might try watching this video:​

Video: Testing for Mold Toxicity

Why Is It Important To Look Out For Mold Exposure Symptoms?​

It is essential to be aware of what mold exposure symptoms look like because mold is surprisingly common in our homes and workplaces. Studies have found that as many as half of the buildings we live and work in have water damage and therefore mold present (Mudarri & Fisk, 2007; Spengler et al., 1994). It is clear that people working in environments with more mold report more mold exposure symptoms (Park et al., 2004) and that people living in homes with more mold experience a range of debilitating mold exposure symptoms (Crago et al., 2003).
 
Another important reason to be aware of mold exposure symptoms is that mold exposure is related to rates of asthma (Portnoy et al., 2008). This does not mean that mold exposure causes asthma, but it may instead cause symptoms to develop or worsen in people who were at risk for asthma or already had it.​

Causes of Mold Exposure Symptoms

How exactly does mold impact our health? There are at least three ways it may impact us (Bush et al., 2006). Mold can irritate our immune system, such as through an allergic reaction; it can directly infect our bodies; or it may cause us harm through the mycotoxins it releases into the air.
​
This last pathway to mold exposure symptoms seems to have the least scientific support, to the point that many scientists debate whether we can truly inhale mycotoxins to the point that we will get sick (Khalili & Bardana, 2005). These scientists note that if breathing in irritants from mold is the cause of our symptoms, the symptoms should lessen or disappear as soon as we get away from the mold itself. However, most mold exposure symptoms are longer-lasting and more consistent than this, suggesting – as research has found – that when people believe their symptoms come from inhaling mycotoxins, they are actually having symptoms related to other, preexisting medical concerns (Khalili & Bardana, 2005).​

Mold Toxicity Symptoms vs Mold Allergy

Some people have mold allergies, meaning their bodies overreact to exposure to mold, relative to the bodies of people without mold allergies (Khalili & Bardana, 2005). At the same time, enough exposure to mold can cause most any person to experience the symptoms of mold toxicity or mold exposure (Gray et al., 2003). People who are continually exposed to mold (test yourself here) develop chronic inflammation in their bodies, which in turn increases their sensitivity to dampness and mold (Valtonen, 2017).​

Can Mold Spores Cause Mold Exposure Symptoms?

Yes, mold spores are a part of how mold reaches our bodies and causes mold exposure symptoms (EPA, 2008). These spores, when we are exposed to them for long periods of time or in great concentrations, do seem to cause symptoms such as nausea, headaches, and irritation of the nose, as well as many of the other symptoms discussed above.​

Mold in House or on the Ceiling

Mold is likely to develop in our houses if they are not routinely cleaned or dehumidified (Sun et al., 2022). Older homes, as well as those with carpeting, pets, and low rates of cleaning the floor, are more likely to have mold present. For people with asthma, living in a home with these characteristics may be associated with more intense asthma symptoms (Tischer et al., 2011; Zock et al., 2002).​

What exactly does mold look like in our homes? 

​One common type, known as penicillium (which is what the medication penicillin is derived from), may appear as a light green spot on both building materials and fabrics in high humidity or damp environments (Andersen et al., 2011). It may also be identified by a musty smell in the air.

Mold Detection Kit

Mold is commonly the result of water damage in buildings (Gravesen et al., 1999), but this may be hard for us to detect as non-experts. For this reason, if you believe there may be mold in your house, purchasing a mold detection kit could be helpful. These kits typically either test the air in your house or take samples from surfaces in your house, such as by applying adhesive strips or brushing cotton swabs against a countertop or windowsill.

Mold Smell

Often, a room may smell moldy, but mold may not be visible – this is still a strong signal that mold may be present (Caillaud et al., 2018). People describe the smell of mold as earthy or musty, perhaps like the smell of a vegetable or fruit that has gone bad or similar to wet dirt.

Mold Cleaning

​Common ways to clean household mold include using steam cleaning or a detergent or bleach wash (Wilson et al., 2004). There is evidence to suggest that washing with detergent or bleach may be the most effective form of treatment (Reynolds et al., 2012). However, if you are sensitive or intolerant to bleach, Decon 30 herbal mold clearer is a pet and people-safe alternative.

​Mold Inspection

A mold inspection is an effective way to discover whether there is mold present in your house. There are many types of mold inspection methods and reports, with varying levels of accuracy, but they are generally understood to be an effective way to determine whether mold is present in one’s house (Horner et al., 2008). As there are no regulations about who can promote themselves as mold inspectors, you might want to carefully consider reviews from prior clients for any mold inspectors you consider.

Articles Related to Mold Exposure Symptoms​

​Want to learn more? Check out these articles:

Books Related to Mold Exposure Symptoms​

If you’d like to keep learning more, here are a few books that you might be interested in.

Final Thoughts on Mold Exposure Symptoms​

Mold exposure symptoms are an important topic to be aware of, but not necessarily something to become actively worried about, especially in dry climates. For people with preexisting sensitivities to their environments, it is probably helpful to consider that both new and persistent physical health problems could be related to mold in their environments, and a personal mold test may be helpful. For people without these sensitivities, mold exposure seems less likely to be a factor in their lives, but it can still be helpful to work actively to keep one’s home environment clean and not too humid.

If you think you may be experiencing mold exposure symptoms, it is probably wise to seek out the input of a medical professional, in addition to conducting at-home testing (Valtonen, 2017). There are many other potential causes of the various health problems associated with mold exposure, and we probably should not jump to the conclusion that mold is to blame without consulting an expert.​

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