A Detailed Look at Mold Allergy

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We are surrounded by mold. Countless species of mold exist in nature and the vast majority are harmless to humans, although terms like “toxic mold syndrome” and “toxic black mold” have been sensationalized in the media. In reality, mold can only cause severe illness in those with weakened immune systems (i.e. immunocompromised).

Mold growing on a wall
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People who work or live in buildings with water damage sometimes complain of “black mold” or “toxic mold.” Instead of the mold is toxic, it’s more likely the mold is causing allergies. Mold typically grows in homes that experience water damage. Importantly, buildings with water damage have been shown to be linked to sick building syndrome, which causes nonspecific symptoms such as fever, fatigue, and nausea.

What Is Mold?

The term “mold” refers to multicellular fungi which grow as a mat composed of intertwined microscopic filaments. Mold is a part of the circle of life, and it decomposes decaying matter.

Here are the most common molds found in homes and other buildings:

  • Alternaria
  • Aspergillus
  • Cladosporium
  • Penicillium

Less common indoor molds include the following:

  • Fusarium
  • Stachybotrys
  • Trichoderma

Typically, mold grows in buildings that have sustained substantial water damage from leaks, flooding, and so forth. Mold can also grow in buildings that contain potted plants or those polluted with animal urine.

Mold Allergy

The link between mold and respiratory illness has been of interest for centuries. In the eighteenth century, James Bolton first hypothesized a causal link, and, in the nineteenth and twentieth centuries, a handful of other scientists followed suit. Over time, there’s been enough evidence-based research done that most clinicians agree that mold plays a role in allergy.

The most common symptoms of mold allergy are hay fever (i.e. allergic rhinitis) and asthma. People with atopy are at a slightly higher risk for mold allergy. Atopy refers to a genetic predisposition to develop allergic illnesses such as asthma, eczema, and allergic rhinitis (i.e. hay fever).

People who are allergic to mold are usually allergic to other things, including:

  • Animal dander
  • Dust mites
  • Grass pollens
  • Tree pollen
  • Weed pollens

In more technical terms, mold allergy, like an allergy to animal dander, grass pollens, and so forth, is an IgE-mediated hypersensitivity reaction. As with other allergens, skin testing can be used to help demonstrate allergy to mold. Furthermore—as with other common allergens— radioallergosorbent testing (RAST) can be used to determine levels of serum-specific IgE antibodies to fungi in the blood.

In a 2005 article published in the Annals of Allergy, Asthma & Immunology, Edmondson and co-authors studied 65 participants between the aged between 1.5 years and 52 who presented to asthma and allergy clinic complaining of “toxic mold exposure.” Of the participants, 53 percent had skin reactions to mold during allergy skin testing.

Here are the chief complaints among the participants in order of decreasing frequency:

  • Hay fever
  • Cough
  • Headache
  • Respiratory symptoms (coughing, wheezing, etc.)
  • Central nervous system
  • Fatigue

Although these symptoms are nonspecific and generalized, on physical examination the researchers observed pale mucous membranes, cobblestoning, and runny nose, which are all signs of allergy.

Having a history of respiratory symptoms—like asthma—that are specific to a certain building supports a diagnosis of mold allergy. On a related note, if you are experiencing such symptoms, it’s important to share with your allergist specifics about your home, work, or school environments. Tracking your symptoms for two weeks in a journal can help determine which environments cause allergy.

Aside from an IgE-mediated immune response, it’s been hypothesized that other constituents in mold could play a role in mold-related illnesses. Culprits include mycotoxins, which are byproducts of mold, and glucans, which make up the cell walls of the mold. Additionally, molds produce volatile organic compounds (VOCs)—such as low-molecular-weight ketones, alcohol, and aldehydes—that have been implicated in mold-related illness. Incidentally, it’s these VOCs that give mold its musty, noxious odor.

However, there is no evidence supporting that non-IgE-mediated mechanisms play a role in low-level exposure to mold. In other words, although mold causes allergies and is an allergen, we don’t have any evidence that after routine exposure the other stuff in the mold can make people sick.


There is no specific medical treatment for mold allergy. However, asthma and hay fever, which results from mold allergy, can be treated using a variety of prescription and over-the-counter medications, respectively. If possible, it’s best to avoid a building that may be triggering your mold allergy. However, this option is not always realistic.

If you have mold allergies and you are going to enter an environment that you suspect harbors mold, you can wear a dust mask. As a preventive measure, you can take allergy medications before you enter the environment.

Buildings can be tested for mold. Indoor air samples can be compared with outdoor air samples to determine mold levels. Furthermore, bulk, wipe, and wall cavity samples can also be taken to detect for mold in buildings, but these samples can’t determine how much mold is respired by occupants.

Link With Sick Building Syndrome

Mold, which is closely tied to water damage, can be an irritant that leads to sick building syndrome. Unlike the name implies, sick building syndrome describes situations where occupants feel sick because of a building’s poor air quality—with increased humidity and decreased ventilation being chief contributors. In addition to water damage and mold, other causes of sick building syndrome include dust, insulation, and poorly maintained heating, ventilation, and air-conditioning (HVAC) systems.

Although sick building syndrome is not formally recognized as an evidence-based medical diagnosis, certain organizations warn of its existence, including the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA). Sick building syndrome is a contentious topic, and when presented with nonspecific, building-related symptoms in a clinical setting, some physicians will treat the problem with antidepressants.

Here is some general preventive guidance for sick building syndrome that also applies to mold allergy:

  • Properly regulate temperature and humidity levels.
  • Identify areas affected by water damage.
  • Ensure that the building is clean.
  • Check all air humidifiers, air filters, and cooling towers.
  • Try to keep windows open for better ventilation.
  • Take breaks from the indoor environment to go outside and walk around.

Here is some specific guidance from the American College of Asthma, Allergy & Immunology regarding the prevention of mold allergy:

  • Clean up any spills or leaks immediately.
  • Clean your gutters and garbage cans.
  • Use refrigerator drip pans.
  • Open windows for ventilation in damp environments like the bathroom
  • Use dehumidifiers or exhaust fans in damp environments like the bathroom.

Buildings that are polluted with mold can undergo remediation, with repairs made to decontaminate the building. In addition to causing allergy and bad odors, mold can also destroy the building materials that it impregnates. Here are some general steps to take when remediating a building.

  1. The source of humidity, which promotes the mold growth, must be completely removed from the house. For instance, if the HVAC system is responsible for mold growth, it needs to be removed.
  2. Carpeting, drywall, or other contaminated building materials need to be removed from the building and replaced.
  3. All upholstery and clothing (porous materials) must be completely washed or dry-cleaned. If these items continue to smell after a thorough cleaning, they need to be discarded.

Industrial hygienists and structural engineers can be contracted to evaluate a building for mold exposure.

In work environments, it’s a good idea to take pictures of water damage and approach management regarding concerns over mold exposure. Alternatively, OSHA or the EPA can be contacted for an air-quality investigation.

Mold Immunotherapy

Immunotherapy refers to the treatment of disease using substances that stimulate the immune system. Allergy shots are a form of immunotherapy given to treat or prevent reactions in people who are allergic to trees, grass, weeds, dander, dust, and so forth. There has been limited research on the topic of mold immunotherapy. Currently, however, immunotherapy for mold allergy is generally not recommended.

In addition to there being a paucity of randomized controlled trials examining mold immunotherapy, studies have only focused on two types of mold: Alternaria and Cladosporium. Furthermore, molds contain proteases (a type of enzyme) that make them bad candidates for immunotherapy


Buildings that are waterlogged after hurricanes or floods are at invariable risk for contamination with mold. Mold is carried in flood water. In these unfortunate circumstances, immediate action is necessary to prevent mold growth. People with atopy, asthma, or weakened immune systems should not be involved in mold remediation.

The CDC makes specific recommendations detailing how to rid a house of mold after a flood, including the following:

  • Assume that any item submerged in water for more than two days is contaminated with mold.
  • Leather, wood, paper, and carpet can’t be ridden of mold and need to be disposed of.
  • Use bleach to clean mold off floors, stoves, sinks, flatware, plates, tools, and other hard objects.
  • When preparing the bleach solution, mix bleach and water in equal amounts.
  • Don’t mix bleach with ammonia or other cleaners.
  • While using bleach, keep the windows open.
  • Wash smaller items with bleach and then rinse these items with water. Then, leave them outside to dry.
  • Use brushes to scrub the surfaces of rough objects.
  • When cleaning for mold, personal protective equipment should be worn, including goggles, rubber gloves, rubber boots, and a tight-fitting respirator.

A Word From Verywell

Although claims of “toxic mold syndrome” and “black mold” are exaggerated, many people are allergic to mold. Currently, there is no specific treatment for mold allergy, with avoidance of the offending indoor environment the only surefire prevention. However, asthma and hay fever, which are symptoms of mold allergy, can be treated.

If you think that you may be suffering from a mold allergy, it’s a good idea to meet with an allergist. An allergist can test your skin or blood for antibodies to common types of mold and make specific recommendations based on your situation.

Building remediation may also help expel the source of mold growth from a building. Affected building materials should also be replaced. However, such repairs can be costly, and it’s best to consult with mold remediation professionals before engaging in these measures.

Finally, flooded structures are invariably contaminated with mold. It’s important to take immediate action when remediating such structures to prevent further mold growth.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Naveed Saleh, MD, MS
Naveed Saleh, MD, MS, is a medical writer and editor covering new treatments and trending health news.