Allergic Asthma Triggered by Mold

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It's not uncommon for people to be unaware that their home has a mold problem. If you have allergic asthma and a mold allergy, however, your body may sound an alarm. Mold spores are microscopic and easily airborne, and breathing them in can trigger symptoms and prompt severe asthma attacks in those with these two conditions.

If you find that your asthma is suddenly worsening and you can't pinpoint why, mold may be to blame. And since reactions can be quite serious, it's important to remedy the problem right away.

Mold Exposure-Related Symptoms

Theresa Chiechi / Verywell

Mold Exposure-Related Symptoms

Asthma and allergy symptoms related to mold exposure are generally the same as symptoms caused by any other trigger:

Because you may easily associate your symptoms with already-familiar exposures that affect your allergies and asthma, like pollen, mold can be overlooked as a possible culprit.

Timing May Be a Clue

If you typically only have seasonal allergies (hay fever) and suddenly start having symptoms inside and off-season, they may be due to mold.


Some types of mold can be hazardous to anyone's health, as they can release harmful toxins. But the reaction to mold that occurs due to allergies and asthma is different.

It occurs because the immune system mistakenly identifies mold (even a type that is normally harmless) as a threat and launches an attack. Increased production of mucus and watery eyes are your body's attempts to flush out the allergen.

With allergic asthma, the response goes even further. The immune system releases cells and chemicals that lead to inflammation and constriction in the bronchial tubes (airways). This is what leads to difficulty breathing.

Some molds that have a known association with allergies and asthma include:

  • Alternaria
  • Aspergillus
  • Cladosporium


While any airborne mold can worsen asthma, allergy to the mold Alternaria has been associated with severe asthma exacerbations.

Alternaria is found almost everywhere, including the air and soil. It's mostly an outdoor mold.


Aspergillus is a common indoor and outdoor mold. Most people come in contact with it without incident on a daily basis. However, for those with asthma who have an allergy to it, this mold can trigger asthma attacks.

While an allergic reaction is a more common reason for experiencing symptoms related to Aspergillus, some people develop a chronic disease called allergic bronchopulmonary aspergillosis (ABPA) due to exposure.

ABPA causes a severe allergic reaction within the lung, which can lead to bronchiectasis—a chronic condition involving inflammation and infection of the airways. Flare-ups of ABPA cause breathing problems that are similar to asthma.


Cladosporium can appear as brown, black or green spots and can grow both indoors and outdoors. Spores can be airborne and affect the airways.

Signs of Mold Exposure

Only a healthcare provider can confirm that mold is causing your symptoms, but awareness of exposure can help put the possibility on your (and their) radar.

Mold thrives in damp, dark, and warm environments. If conditions are right, it can grow on all kinds of surfaces, including walls, floors, fabrics, and plants.

Water spills, leaks, seepage, and condensation can be to blame, and as such, mold often starts due to issues such as:

  • High humidity
  • A roof leak
  • Pipe/faucet leaks
  • Floods
  • Poor ventilation in a bathroom or kitchen
  • Wet carpeting
  • Broken seals on windows

Some of these may be obvious to you, but others can easily occur without you knowing (at least not right away). Through spores, mold can travel not only through the air, but from one damp area to another—and quickly.

Signs you should not ignore, which could indicate mold, include:

  • A musty odor
  • Discoloration of a wall, ceiling, or other surface that's had prior water damage
  • White, orange, green, or black growth in a moist area

If you've had a home issue that could result in mold or you notice any of these signs, and your allergies/asthma are worsening without explanation, it's important that you get evaluated by your healthcare provider.


If you haven't been diagnosed with asthma, your healthcare provider will likely perform multiple tests to confirm or rule it out as a cause of your symptoms.

Then, to explore whether mold is the reason behind allergic asthma symptoms, further testing may be recommended.

Possible tests include:

  • Skin test for allergies: Your skin is punctured or scratched and a small amount of mold is placed there to see if you react to it.
  • IgE ImmunoCAP tests to mold: This blood test evaluates how your immune system responds to mold.

Additionally, if you or your healthcare provider suspect ABPA, you'll be given blood tests to determine whether you have it or you are just experiencing an an allergic reaction.


Treatment for mold-triggered allergic asthma should include managing your symptoms and avoiding future exposure whenever possible.

Managing Symptoms

Generally, asthma and allergies are treated the same regardless of the cause. A rescue inhaler, long-term asthma control medications (if prescribed), and antihistamines should help relieve symptoms.

However, certain mold reactions may require additional treatments, such as ABPA treatment. This often requires oral corticosteroids and may also include anti-fungals. Other therapies for severe asthma are frequently used in conjunction with these medications.

If you're being exposed to mold outside, you may want to wear a mask or respirator so you're not inhaling allergens. That may also be necessary in indoor spaces you can't control, such as a store or someone else's home.

Removing Mold

It's important to get rid of mold in your home and take steps to keep it from coming back.

First, you need to figure out where it is growing, if not known already:

  • Look in high-moisture areas like the kitchen, bathrooms, laundry room, and basement.
  • Assess visible pipes and check rooms with pipes in the walls for staining/smells.
  • If a room smells musty, you may have mold growing somewhere hidden like behind wallpaper, tiles, or inside a wall. You may need to open things up to take a look.

To eradicate any mold you find:

  • Wash the affected areas with detergent and water and let it dry completely.
  • Replace certain materials that hold moisture (e.g., sheetrock, ceiling tiles, carpet).
  • Make sure any areas you are working in are well ventilated or you may increase your acute exposure to molds. Wearing a mask is recommended.

According to the Federal Housing Administration (FHA), you may be able to handle a simple problem like mildew in the bathroom, but a professional may be advisable for more involved jobs, especially if:

  • You can't identify what type of mold you're dealing with
  • You're having trouble identifying the cause(s) of the mold
  • The mold is covering a large area (anything larger than 10 square feet)

Hiring a professional is also necessary if your own attempts to remove the mold are unsuccessful.

Mold in Rentals or at Work

Laws are in place to protect you from hazardous exposures in rentals and on the job. If there are any concerns about mold in your workplace or rental, make sure the responsible person—the property manager, owner, your boss—is made aware of them.

Preventing Mold

Mold reduction in the home is associated with significant improvements in asthma symptoms among people who are sensitive to molds. But if mold grew once, it can grow again.

To make sure it doesn't come back:

  • Keep relative humidity under 50%. This may require air conditioning or a dehumidifier.
  • Avoid carpet in areas like bathrooms.
  • Consider using paint that is "mold-resistant."
  • Repair any leaks inside and outside the home. Dry any wet areas thoroughly.
  • Put plastic over dirt crawl spaces and make sure they are well ventilated.
  • Limit the number of indoor plants.
  • Keep drip pans in refrigerators and air conditioners clean and dry.

Ventilation is particularly important. The current trend in home building and remodeling is to make houses "airtight." That's good for energy efficiency, but it makes houses more likely to harbor mold than older houses that "breathe" more.

To improve ventilation:

  • Consider adding roof vents to allow air to escape.
  • Consider adding exhaust fans to push moisture from clothes dryers, stoves, and other appliances out of your home.
  • Likewise, install a vent in your bathroom, if you don't have one already. Run it when showering to reduce moisture build-up from steam.
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.
  1. Asthma and Allergy Foundation of America. Mold allergy.

  2. Asthma and Allergy Foundation of America. Mold Allergy.

  3. Al-Ahmad M, Jusufovic E, Arifhodzic N, Rodriguez T, Nurkic J. Association of molds and metrological parameters to frequency of severe asthma exacerbation. Allergy, Asthma & Clinical Immunology. 2019;15(1). doi:10.1186/s13223-019-0323-8

  4. National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. Aspergillosis.

  5. American Lung Association. What Causes Bronchiectasis?

  6. U.S. Department of Housing and Urban Development. About Mold and Moisture.

  7. Knutsen A, Slavin R. Allergic bronchopulmonary aspergillosis in asthma and cystic fibrosis. Clinical and Developmental Immunology. 2011;2011:1-13. doi:10.1155/2011/843763

  8. U.S. Federal Housing Administration: Should I hire professional mold removal?

Additional Reading

By Daniel More, MD
Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California.