An Overview of Mold Allergies

Mold can cause allergy and non-allergic fungal infections

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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.

moss and mold on wall
 User51580df0_522 / Getty Images


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

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 healthcare provider. You may notice some trends that help you discover what is triggering your allergic reaction.

Your healthcare provider 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.

If you see or smell mold in your home, clean-up is recommended (often with professional help to avoid personal exposure). Fixing any water leaks that are allowing excess moisture is imperative to decrease likelihood of future mold growth.


Mold allergies can be treated. When eliminating exposure is not possible, allergy treatments can be used. Intranasal corticosteroids are effective in treating most nasal symptoms of mold allergy. They may also help some eye symptoms. These work best after they have been used consistently for a couple of weeks.

Antihistamines can also be taken; non-sedating antihistamines start working within an hour and can last for 24 hours. They do not usually control symptoms as well as intranasal corticosteroids, and many people add intranasal corticosteroids to their antihistamine of choice if they are still noticing allergy symptoms.

Allergy shots to treat mold allergy have not been shown to be as effective as allergy shots to certain common pollen allergens, but many allergists will prescribe them, particularly if there are also other types of allergens causing symptoms.

Allergic bronchopulmonary aspergillosis is a severe lung disease and oral corticosteroids are usually required.

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, including:

  • 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 appropriate cleaning agents, while using appropriate protective gear. For large contaminated areas, professional remediation is recommended to avoid personal mold exposure.
  • 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 for people without asthma, 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.

6 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. Amirhosein Ghaffarianhoseini, Husam AlWaer, Hossein Omrany, Ali Ghaffarianhoseini, Chaham Alalouch, Derek Clements-Croome & John Tookey (2018) Sick building syndrome: are we doing enough?. Architectural Science Review,61:3, 99-121.

  2. American College of Allergy, Asthma & Immunology. Mold Allergy. Reviewed April 23, 2018.

  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.

  6. Centers for Disease Control and Prevention. Molds in the Environment. Rreviewed December 20, 2017.

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.