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May 24, 2023

Mold Allergy: Symptoms, Causes, and Treatment

Daniel More, MD, is a board-certified allergist and clinical immunologist with a

Daniel More, MD, is a board-certified allergist and clinical immunologist with a background in internal medicine.

Corinne Savides Happel, MD, is a board-certified allergist and immunologist with a focus on allergic skin disorders, asthma, and other immune disorders.

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.

Theresa Chiechi / Verywell

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.

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:

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.

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:

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:

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:

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.

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.

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:

To eradicate any mold you find:

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:

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

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.

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:

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:

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

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

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By Daniel More, MDDaniel 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.