How Mold Affects Your Respiratory System

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Mold is a type of fungus you can find outdoors and indoors. There are many types of mold—about 1,000 in the United States—but we don’t often come across many of them. The most common molds found inside buildings—in walls, bathrooms, floors, and other damp spaces—are Cladosporium, Penicillium, and Aspergillus.

Molds also spread by sending spores into the air that can travel a long distance before settling down somewhere else.

Mold can have serious effects on your health if you breathe in the spores. This occurs most often if you disturb mold, sending the spores into the air in large numbers. This is one reason why people who tear down walls wear masks. The masks reduce exposure to the spores over a long period. Masks are also beneficial if you live in a building that has a significant amount of mold.

Learn about how mold can affect your respiratory health and who is at higher risk.

Mold Respiratory Symptoms

Breathing in mold spores can cause serious short- and long-term problems that have an impact on how well you can breathe. For generally healthy people, the most common symptoms associated with being exposed to mold are:

  • Stuffy nose
  • Red, itchy eyes
  • Itchy skin

These symptoms relate to immune hypersensitivity, or allergic reaction to mold. If you have asthma or an allergy to mold, your reactions may be much stronger than the average person. Even short exposure could trigger asthma symptoms. While mold is a fungus, most people who have an allergic reaction to mold are treated with steroids and antihistamines—not antifungal medication.

The people who are most likely to inhale large amounts of mold spores are those who work on or who work indoors, rehabbing old buildings and cleaning out attics and areas where mold may grow. People at high risk of contracting a mold-related illness, particularly from indoor mold, are people with chronic lung conditions (such as COPD) or weakened immune systems. A compromised immune system, whether it’s due to medications (like chemotherapy or organ transplant anti-rejection drugs) or you don’t have a spleen, puts you at higher risk for any type of infection.

The Mold and Asthma Connection

No matter how well controlled your asthma may be, exposure to mold spores can trigger asthma symptoms, especially if you have a mold allergy. As the spores enter your lungs, your immune system responds to fight them, releasing immune cells and chemicals like histamine. The result is your airway may constrict (tighten up), making it hard to breathe. Your respiratory system may also start producing more mucus, in an effort to get the allergens (spores) out of your lungs.

Mold may affect young children differently from adults. A study published in 2018 found children exposed to mold may develop asthma later in life.

Protecting Yourself from Mold

To prevent mold growth:

  • Control humidity in your home (guideline is 30 to 50% humidity)
  • Ventilate kitchens, showers and laundry rooms
  • Maintain pipes, window seals, and roofs, checking regularly for cracks and leaks

If you discover mold in your home, the first step is determining why it is growing. There is usually a problem with dampness and moisture, such as from a leak. You can hire a professional or investigate and fix the problem yourself. While working, protect your airways from the spores with a respirator, such as an N95 mask.

The second step is removing and replacing moldy items, such as carpet, furniture and drywall if necessary. You can clean hard items like shower stalls with a mixture of bleach and water (1 cup bleach to 1 gallon water). Wear a respirator for cleaning as well. Thoroughly dry the area.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Jul 9
  1. Mold Course Chapter 1. United States Environmental Protection Agency.
  2. Basic Facts about Mold and Dampness. Centers for Disease Control and Prevention.
  3. Mold. Centers for Disease Control and Prevention and National Center for Environmental Health.
  4. Mold and Dampness. American Lung Association.
  5. Mold allergy. Mayo Clinic.
  6. Mold 101: Effects on Human Health. Poison Control; National Capital Poison Center.
  7. Mold Allergy. American College of Allergy, Asthma & Immunology.
  8. Caillaud D, Leynaert B, Keirsbulck M, Nadif R. Indoor mould exposure, asthma, and rhinitis: findings from systemic reviews and recent longitudinal studies. European Respiratory Review. 2018 27: 170137; DOI: 10.1183/16000617.0137-2017
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