Mold allergy: symptoms, testing and treatment

What is a mold allergy?

A mold allergy is an immune overreaction to mold spores. The American Academy of Allergy, Asthma & Immunology (AAAAI) explains that everyone breathes in mold spores, but in people with a mold allergy, the immune system treats certain spores as an allergen and triggers symptoms. It is the same basic process as hay fever from pollen.

Molds are tiny fungi whose spores float through the air, indoors and out. AAAAI says they need four things to grow: food, air, the right temperature and water. Of the hundreds of mold types, AAAAI says not all cause allergy symptoms. The most common allergy-causing molds are Alternaria, Aspergillus, Cladosporium and Penicillium. CDC lists Cladosporium, Penicillium and Aspergillus as the most common molds found indoors, so the overlap is large. Our glossary has short entries on Aspergillus and Cladosporium.

A mold allergy is different from mold irritation, which EPA says can affect the eyes, skin, nose, throat and lungs of people who are not allergic at all. It is also different from the contested idea of “toxic mold” illness. For the full picture of what indoor mold can and cannot do to health, see our mold symptoms guide, and for identification and cleanup, start at our mold hub.

What are the symptoms of a mold allergy?

AAAAI lists the main mold allergy symptoms as:

• Itchy nose, mouth and lips
• Sneezing
• Itchy, watery eyes
• Runny nose
• Nasal congestion

EPA describes the same hay-fever-type reactions and adds skin rash (dermatitis). EPA says allergic reactions to mold are common and can be immediate or delayed, which is one reason people sometimes do not connect their symptoms to a damp basement or a leak.

Where and when symptoms show up is a clue. AAAAI says many people with mold allergy notice symptoms outdoors on days when mold spores are in the air, and may also have symptoms indoors if there is mold in their home, school or workplace.

AAAAI is direct about what mold allergy usually does not do: it “is not usually a cause of chronic symptoms such as headache and fatigue.” The Institute of Medicine’s 2004 review likewise found inadequate evidence linking indoor mold to fatigue or neuropsychiatric symptoms. If those are your main complaints, they are not supported by current evidence as mold effects, and a doctor should look for other causes.

How is a mold allergy different from other mold reactions?

The table below compares the reactions that agencies and medical groups describe, so you can see why an allergist’s evaluation matters.

Allergy and irritation can feel similar. The difference is the immune mechanism, and only testing can confirm an allergy.

How does mold affect asthma?

For people with asthma, mold is a recognized trigger. EPA says molds can cause asthma attacks in people with asthma who are allergic to mold, and advises people with asthma to avoid contact with or exposure to molds. AAAAI says mold allergy can trigger asthma symptoms such as wheezing, shortness of breath and chest tightness.

The evidence here is among the strongest in the mold-health literature. The Institute of Medicine’s 2004 review found sufficient evidence of an association between indoor mold and asthma symptoms in sensitized people, meaning people whose immune systems already react to mold. CDC says people with asthma or a mold allergy may have severe reactions.

Whether mold can cause asthma to start in the first place is less settled. IOM rated asthma development as limited or suggestive evidence for damp indoor environments, and inadequate evidence for mold specifically. CDC notes newer studies suggesting early mold exposure may be linked to asthma development in some children, especially those who may be genetically susceptible.

If you have asthma and live with mold, CDC says you should not stay in the moldy home or be present while it is cleaned. Keep your asthma action plan current with your doctor, and treat moisture problems quickly.

How do you get tested for a mold allergy?

See a board-certified allergist/immunologist. AAAAI says symptoms of mold allergy often mimic other conditions, and that an allergist can determine whether mold is responsible.

The most common test is a skin prick test. AAAAI describes it as the most common and reliable form of allergy testing: a tiny amount of allergen is introduced into a small prick on the skin, and reactions appear within about 15 minutes. A small swelling at a test spot shows sensitivity to that allergen. AAAAI says blood tests are generally used when skin testing might be unsafe or will not work, such as when someone takes certain medications or has a skin condition.

Two cautions. First, AAAAI warns that some tests are offered by practitioners without formal allergy training, and that it and other professional bodies recommend against IgG testing to diagnose food allergies or sensitivities. ACMT adds that fungal antibody tests can help with allergies and hypersensitivity pneumonitis but give no information about mycotoxin exposure. Second, the Connecticut Department of Public Health notes that a positive skin test shows you were exposed at some point; it cannot show where or when. Urine “mold toxicity” tests are a separate product; see our page on mycotoxin urine tests.

How is a mold allergy treated?

AAAAI says avoiding exposure is the best way to manage mold allergy symptoms. Its avoidance advice includes:

• Stay indoors on days when mold counts are high, and check counts through the AAAAI’s National Allergy Bureau.
• Avoid uncut fields and raking leaves.
• Shower after coming indoors to wash spores out of your hair.
• Fix leaking faucets and pipes to remove indoor mold sources.
• Keep indoor humidity below 60 percent.
• Replace basement carpeting with flooring that does not hold moisture.

On top of avoidance, AAAAI says your allergist may recommend over-the-counter or prescription antihistamines, eye drops or nasal sprays. For longer-term relief, AAAAI describes immunotherapy, or allergy shots: regular injections of small doses of the allergen that help your body build tolerance over time.

Which option fits depends on how severe your symptoms are and how well avoidance works. That decision belongs with your allergist. Our mold prevention guide covers the household side, including humidity targets and ventilation.

How do you reduce mold at home if you are allergic?

Control moisture first. EPA says the key to mold control is moisture control, and that wet materials dried within 24 to 48 hours usually will not grow mold. EPA’s humidity target is below 60 percent, ideally 30 to 50 percent. CDC recommends keeping humidity no higher than 50 percent all day, using an air conditioner or dehumidifier, running kitchen and bathroom exhaust fans that vent outside, and venting the clothes dryer outdoors. Our guide to the best dehumidifiers for mold explains capacity and settings.

When mold does appear, remove it rather than just killing it. EPA notes that dead mold can still cause allergic reactions, so it is not enough to spray it; it has to be cleaned off. EPA says to scrub hard surfaces with detergent and water and dry them, and that porous materials like ceiling tiles and carpet may need to be thrown away.

If you are the allergic one, have someone else do the cleaning. CDC says people with allergies should not take part in mold cleanup. Whoever does it should wear at least an N95 respirator, gloves and goggles; our mold cleanup PPE checklist covers the gear. For patches larger than about 10 square feet, EPA suggests professional help. Our guide to choosing a mold remediation company explains what to ask.