Mold Exposure: Signs, Symptoms, and Complications

Mold exposure doesn't affect everyone in the same way. Some people do not react to mold, while others will have symptoms, especially those with mold allergies. Symptoms may include congestion, wheezing, and red, itchy eyes and skin.

This article explains common and rare mold exposure symptoms plus complications that can occur.

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Some species of mold can trigger allergies and asthma. Mold grows in dark, damp places, like basements, around sinks, roofs, windows, and areas with standing water. The most common indoor molds are Cladosporium, Penicillium, and Aspergillus.

Mold allergy symptoms include:

Like other allergies, mold allergy can develop at any age. Symptoms of mold allergy may appear immediately upon exposure, or they may be delayed. When symptoms are delayed, it can sometimes make an association between the allergen and symptoms less clear.

In addition to allergies, mold can trigger allergic asthma symptoms in some people. These symptoms include:

When you have asthma, several changes in your airways occur, making breathing difficult, such as swelling, excess mucus, and muscle contraction. Asthma can usually be managed, but asthma attacks can also be life-threatening.

More rarely, mold exposure can cause other symptoms. These include:

These symptoms may be signs of rare conditions that develop from mold exposure.

Hypersensitivity pneumonitis is an immune system disorder that develops from a reaction to an inhaled allergen. It results in flu-like symptoms, like fever, chills, body aches, and headache. This condition is usually acute, developing within hours of exposure. However, about 5% of people develop a chronic condition. This condition is treated by eliminating the allergen.

Certain people are more at risk for developing hypersensitivity pneumonitis, including farmers and cattle workers routinely exposed to mold in hay and grain and people exposed to humidifier fungus. However, even among these higher-risk groups, 85% to 95% of people will not develop the condition.

Allergic bronchopulmonary aspergillosis (ABPA) is an allergy to a fungus found in soil. A person develops an allergic and inflammatory response to mold in this condition. With ABPA, you may experience a cough with bloody mucus, fever, and weakness.

ABPA treatment includes corticosteroids and anti-fungal medications.

Sometimes people can develop a fungal infection when they inhale mold spores. For example, coccidioidomycosis (commonly called Valley fever) is a fungal infection of the lungs. This fungus is found in soil in the U.S. Southwest, Mexico, and Central and South America.

This condition is not contagious and is usually mild. Symptoms appear one to three weeks after exposure and can last up to a few months. Symptoms include:

About 5% to 10% of people will develop long-term complications. People exposed to dust storms and with compromised immune systems are most at risk of developing this condition.

While most people think of "toxic black mold" as causing complications in healthy people without preexisting conditions, that idea has been disproven. There is no scientific evidence that exposure to mold causes autoimmune disease.

There is also no evidence that acute infantile idiopathic pulmonary hemorrhage (bleeding into the lungs), memory loss, or fatigue is due to mold exposure.

However, people with chronic conditions, like immune suppression and asthma, are more likely to experience complications from mold exposure.

After mold exposure, invasive mold infections can occur in people with weakened immune systems. These infections are rare and potentially life-threatening.

People who have had an organ transplant, have cancer, are undergoing cancer treatment, or take medications like biologics or corticosteroids that weaken the immune system are at greater risk of developing invasive mold infections.

Symptoms include:

If you have a weakened immune system, it is important to avoid places with known mold and to avoid mold cleanup. If you must enter a place with mold, wear an N-95 respirator. If you experience flooding, you should also be careful, as mold usually begins growing within one to two days.

Mold exposure can prompt a severe asthma attack in people with asthma. Sometimes these attacks can be fatal.

Warning signs of an asthma emergency needing immediate medical care include:

Signs of a severe asthma attack in children may be similar to those above and also include unresponsiveness or not recognizing caregivers, nasal flaring, flopping head and body, and irritability.

It is a medical emergency if you or your child experiences these symptoms. You should call 911 immediately.

Whenever you experience allergy or asthma symptoms, it's a good idea to see a healthcare provider, especially an allergist (a doctor specializing in treating allergies) or pulmonologist (a doctor specializing in lungs), for an accurate diagnosis. They will be able to help you figure out which allergens cause you problems so you know the things to avoid. They will also help you develop a plan to manage your allergies or asthma.

If you experience hypersensitivity pneumonitis, ABPA, or fungal infection symptoms, seek medical attention since some conditions can become chronic and often require medical treatment.

Mold exposure does not cause symptoms in everyone. However, in people with allergies and asthma, they may cause allergy symptoms and asthma attacks. More rarely, some people may develop flu-like symptoms after inhaling the allergen. These symptoms may be due to hypersensitivity pneumonitis, ABPA, or fungal infection. Complications most often occur in people with compromised immune systems and people with asthma.

Centers for Disease Control and Prevention. Basic facts about mold and dampness.

Borchers AT, Chang C, Eric Gershwin M. Mold and human health: A reality check. Clin Rev Allergy Immunol. 2017;52(3):305-322. doi:10.1007/s12016-017-8601-z

Asthma and Allergy Foundation of America. Mold allergy.

Asthma and Allergy Foundation of America. Asthma symptoms.

Asthma and Allergy Foundation of America. Allergic bronchopulmonary aspergillosis (ABPA).

American Lung Association. Hypersensitivity pneumonitis symptoms and diagnosis.

American Lung Association. Learn about hypersensitivity pneumonitis.

American Lung Association. Learn about coccidioidomycosis.

Chang C, Gershwin ME. The myth of mycotoxins and mold injury. Clin Rev Allergy Immunol. 2019;57(3):449-455. doi:10.1007/s12016-019-08767-4

Centers for Disease Control and Prevention. Invasive mold infections in immunocompromised people.

By Kathi ValeiiAs a freelance writer, Kathi has experience writing both reported features and essays for national publications on the topics of healthcare, advocacy, and education. The bulk of her work centers on parenting, education, health, and social justice.