The Fungus Among Us: The Truth About Household Mold and Your Lungs

Household mold – that fuzzy little fungus that lurks in the most mysterious places in your home has been attributed to the cause of everything from headaches to asthma. For years, mold has been at the center of many a heated debate between allergists and scientists alike. But is there actual scientific evidence to back up claims that indoor mold causes undisputable physical symptoms? Take a look at what the latest research says and decide for yourself:

The Institute of Medicine

In 2004, the Institute of Medicine (IOM) found sufficient evidence linking indoor mold exposure and dampness to upper respiratory symptoms, cough and wheeze in otherwise healthy people, and with asthma symptoms in people with asthma. In addition, they reported a link between indoor mold exposure and hypersensitivity pneumonitis (redness and swelling of the lungs from breathing in foreign substances such as dust, mold, and chemicals) in people who were susceptible to this condition.

Equally, IOM found little evidence linking indoor mold exposure to respiratory illness in otherwise healthy children, and limited evidence to support the claim that exposure to damp, indoor environments causes shortness of breath, respiratory illness in otherwise healthy children, or the development of asthma.[1]

Johns Hopkins University School of Medicine

In 2008, allergists at Johns Hopkins University School of Medicine in Baltimore, Maryland issued a report entitled “9 Common Mold Myths” that set out to prove what health conditions could, and could not be, associated with mold exposure. Some of their most important findings are included below:[2]

  • Toxic Mold – If you listen to the news, you’ve probably heard the term “toxic mold” floating around on the airwaves. But experts say that this term can be misleading. The truth is, you are more likely to ingest toxic mold from severely contaminated food than inhale it. Moreover, not all mold spores produce toxins and just because they can produce them doesn’t mean they will. Only some mold spores produce toxins and then only under certain, specific conditions. Even if mold does produce toxins, you must inhale a sufficient amount of mold spores to be affected. In conclusion: there is no evidence to support that toxic mold-related disease stems from inhaling household mold or, that you could breathe in enough mold in your home or office to receive a toxic dose.
  • Mold and Asthma – Mold has been cited as both a trigger and a cause for asthma and asthma-related symptoms. While there’s little debate that allergic reactions to inhaled mold are possible in people with asthma, only about 5% of the population manifest symptoms in response to indoor mold exposure. Outdoor mold exposure is generally much more likely to trigger allergy symptoms in asthmatics than indoor mold exposure. In conclusion, the link between asthma symptoms and inhalation of indoor mold has not been clearly established.
  • Mold and Allergies – Although there is some evidence supporting a cause and effect relationship between indoor mold and allergies, the manifestation of this type of allergic response is usually limited to people who are severely hypersensitive to indoor mold. In addition, the Johns Hopkins study found no clear-cut evidence that indoor mold exposure causes chronic rhinosinusitis (long-term inflammation of the nasal passages and sinuses.)
  • Mold and Infection – Fungal infections, such as toenail fungus, oral thrush, or jock itch, stem from fungi that develop in warm, moist environments like the inside of your shoes, your mouth, or tight under-garments, respectively. Infections such as these are not usually caused by exposure to indoor mold.
  • Mold and Irritation – There’s a whole lot of talk about exposure to indoor mold as being the cause of irritation of the eyes and throat. Is there any validity to this? The experts don’t think so. Allergists at Johns Hopkins report that if irritation occurs at all, it is only temporary. If symptoms persist, they are not likely caused by indoor mold exposure.
  • Mold and the Immune System – Previous studies have suggested a link between indoor mold and damage to the immune system. Johns Hopkins reports that no credible evidence exists linking environmental mold exposure to immune system damage. Furthermore, the allergists advise against getting tested for sensitivity to mold and other substances, claiming the tests are expensive and incapable of providing useful information pertaining to the diagnosis and management of mold-related diseases.

The World Health Organization

Poor indoor air quality has long been believed to be a contributing factor to ill health. From pollen and spores of plants (mainly from outdoor sources) to microbes, allergens, bacteria, mold, and algae, it’s a wonder that we make it out of our homes alive!

In 2009, the World Health Organization (WHO) conducted a review of the existing evidence related to indoor mold, dampness and illness. Although WHO identified a number of indoor substances for which specific air quality guidelines was recommended, they found no clear evidence establishing that indoor mold and dampness causes any of the health conditions reviewed in their study (asthma, bronchitis, respiratory infections, upper respiratory symptoms, etc.). However, WHO did find an association between indoor mold and dampness and:

  • Asthma symptoms (in people who were severely hypersensitive to mold/dampness)
  • Respiratory infections
  • Upper respiratory tract symptoms
  • Cough
  • Wheeze
  • Shortness of breath
  • Hypersensitivity pneumonitis (linked to indoor mold exposure only)

On the other hand, WHO found little evidence to support that exposure to indoor mold and dampness was associated with bronchitis and allergic rhinitis, more commonly referred to as hay fever. There was also insufficient evidence to support an association between indoor exposure to mold and dampness and altered lung function, allergic asthma, or atopic dermatitis.[3]

Summary of WHOs Indoor Air Quality Guidelines

As the debate over indoor mold exposure lives on, there’s one thing that’s likely to be well understood: when it comes to your lungs, you don’t want to take any chances. The purpose of the WHO report was to establish air quality guidelines that people could use as a way to protect their health.

Because excessive moisture is at the root of all problems related to indoor dampness and mold, the following guidelines emphasize three main actions: detecting and locating sources of moisture in your home, removing mold, and defending your home against excessive moisture and condensation. The following summarizes what steps you should take:[4]

  • Remove mold when it appears. For tips on household mold removal, read the Environmental Protection Agency’s Brief Guide to Mold, Moisture and Your Home.
  • Open windows for short periods of time, at least 2-3 times a day.
  • Maintain and keep your mechanical ventilation system running at all times.
  • Use fans in your bathrooms and kitchen.
  • Prevent rooms and walls from becoming too cold.
  • Immediately repair leaky faucets and other building impairments.

[1]“Facts about Mold and Dampness.” Centers for Disease Control and Prevention. Updated June 17, 2014.

[2] Bush, Robert K. et. al. “The medical effects of mold exposure.” J Allergy Clin Immunol. 2006 Feb;117(2):326-33.

[3]   “WHO Guidelines for Indoor Air Quality: Dampness and Mould.”World Health Organization. 2009.

[4] “Damp and Mould: Health Risks, Prevention, and Remedial Actions. World Health Organization. 2009.


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