An Overview of Mold Allergies

Mold can cause allergy and non-allergic fungal infections

moss and mold on wall
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Mold, also known as fungus, is a type of multicellular organism found throughout nature, as well as indoors. If you have a mold allergy, it can trigger symptoms of hay fever such as a runny nose, cough, and headaches.

An allergic reaction to mold occurs when the body has an immune reaction to mold exposure. Diagnosis can take time, and identifying the source of mold can be challenging. Medications can help alleviate the effects of a mold allergy. If possible, removing the mold or avoiding it once the source is found is the best way to manage the allergy.


You can develop a mold allergy at any age. The symptoms can begin immediately upon exposure. For some people, the effects persist all day, especially if you spend long periods of time around the mold.

Because mold may be present in some buildings, you may feel sick only at certain times, such as after spending a few hours in a mold-infested building. This is often described as "sick building syndrome." However, other issues can cause sick building syndrome—including poor ventilation, dust, and uncomfortable temperatures.

Mold allergies typically cause respiratory symptoms. The effects of a mold allergy include:

  • Coughing, sneezing
  • Stuffy, itchy, or runny nose
  • Itchy, watery eyes
  • Sore throat
  • Wheezing

A mold allergy can trigger an asthma attack if you have asthma. Symptoms may include wheezing and shortness of breath.

Mold allergies are similar to pollen and dust allergies. One of the differences between mold allergies and seasonal allergies like pollen is that you can experience a mold allergy that spans several seasons or lasts all year round.

Mold vs. Fungus

Mold is a type of fungus. Fungal infections are different than mold allergies and can affect the skin, feet, lungs, or even the brain. While anyone can get a fungal infection on the skin (like athlete's foot), fungal infections that invade the body's organs tend to affect people who have an immune problem.

Mold is a living organism, but a mold allergy is not an infection.


Mold allergies are triggered by inhaling spores. Spores are tiny particles that form as mold reproduces, and they can easily travel through the air into your nose, triggering an allergic reaction.

Mold may grow outside or on wood or other building materials, and it generally needs moisture to thrive.

Anyone can be exposed to mold, but some people are more prone to mold allergies. If you have asthma or other types of hay fever, you are more likely to have an allergic reaction to mold too.

Exposure to Mold

In colder climates, molds can be found in the outdoor air starting in the late winter and peaking in the late summer to early fall months (July to October). In warmer climates, mold spores may be found throughout the year, with the highest levels found in the late summer to early fall months.

Indoor mold can come from the outside environment, and indoor mold levels tend to be higher when there is a high level of outdoor mold. Indoor mold contamination can occur year-round and is often dependent on moisture levels in the home.

Flooding and water leaks increase the risk of indoor mold.

Types of Mold

There are many different types of mold and certain types are more common in the air.

Mold-induced allergic disease is most often caused by the following types of mold:

  • Alternaria: A common outdoor mold; allergy to this mold can be associated with severe asthma
  • Cladosporium: The most common airborne outdoor mold
  • Aspergillus: A common indoor and outdoor mold. Also associated with allergic bronchopulmonary aspergillosis, a severe lung reaction that may cause bronchiectasis (severe widening of the bronchi in the lungs)
  • Penicillium: A common indoor mold allergy to which is not associated with antibiotic allergy
  • Helminthosporum: More commonly found in warmer climates
  • Epicoccum: Found in grassland and agricultural areas
  • Fusarium: Commonly found on rotting plants
  • Aureobasidium: Common outdoor mold, commonly found on paper, lumber, and painted surfaces
  • Phoma: An outdoor mold, especially common during wet periods
  • Smuts: Abundantly found in areas of agriculture
  • Rhizopus and Mucor: Commonly found on decaying leaves and damp indoor areas. Airborne forms of these molds are less common
  • Yeasts: Commonly found in the air during wet periods in agricultural areas.

Allergic Reaction

Most spores can be allergens. They induce an inflammatory process in susceptible people. The reaction is mediated by IgE, a protein that rapidly triggers the activation of immune cells.


Mold allergies can be diagnosed based on your symptoms, physical examination, and diagnostic testing.

You might benefit from keeping a diary of your symptoms and talking about it with your doctor. You may notice some trends that help you discover what is triggering your allergic reaction.

Your doctor may also send blood tests, such as an IgE test, to verify that your symptoms are caused by an allergy, and not by an infection.

Allergy testing also includes skin prick tests, in which you would be exposed to an allergen placed on your skin with a needle to see if you have a reaction. There are thousands of types of mold, however, and only a few of these are currently available for allergy testing.

Environmental Testing

There are no well-established guidelines for mold testing in the environment. Mold-induced allergies are based on individual susceptibility, rather than on the quantity or type of mold. According to the Centers for Disease Control and Prevention (CDC), mold sampling is very expensive, and the situation must be interpreted along with an inspection of the contaminated area.

You might want to contact your local health agency to see if they can test your workplace or home for mold and to find out if it has been a problem in your area.


Mold allergies can be treated. You can use anti-allergy medications like allergy shots or antihistamines. In some situations, oral steroids are necessary to relieve the effects of a severe mold allergy such as bronchopulmonary aspergillosis.

There are a number of strategies you can use to help reduce exposure to mold if you or a family member is allergic to mold.

Precautions you can take include:

  • Prevent outdoor molds from entering your home by keeping doors and windows closed and using air conditioning equipped with allergen-grade air filters
  • Control indoor moisture with the use of dehumidifiers
  • Fix water leaks in bathrooms, kitchens, and basements
  • Ensure adequate ventilation of moist areas
  • Clean or replace contaminated surfaces with diluted a chlorine bleach solution (one part household bleach in 9 parts water), while using proper protective gear (mask and goggles)
  • Utilize HEPA-filters on vacuums or as a stand-alone air filter
  • Limit indoor houseplants, and ensure those that are present are free of mold on leaves and in potting soil

Sometimes, it can take a long time to identify the cause of the allergy and to remove or avoid it. In the meantime, mold will not cause a fungal infection. Fungal infections are caused by different molds than the ones that cause allergies, and they spread differently too.

A Word From Verywell

Mold allergies are not uncommon. These allergies can make you feel sick, but the condition is not typically dangerous. While they are frequently confused, mold is not the same as exposure to asbestos, a building material linked to cancer.

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  3. Centers for Disease Control and Prevention. Fungal Diseases. Reviewed May 6, 2019.

  4. Centers for Disease Control and Prevention. Mold. Basic Facts. Reviewed December 20, 2017

  5. Asthma and Allergy Foundation of America. Mold Allergy. Reviewed October 2015.

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