Hidden Danger: How Mold Exposure Affects Your Health

Mold is everywhere. It grows outdoors in soil and on decaying plant matter and can make its way indoors when there is moisture and the conditions are right. Most of the time, short exposure to common household mold does not cause ongoing harm.

But for people with allergies, asthma or a compromised immune system, mold exposure is a serious concern. And prolonged or heavy exposure creates health risks even for people who were previously unaffected.

How Mold Affects the Body

Mold releases tiny spores into the air. You cannot see these spores, but you can breathe them in. Depending on your health and how much mold you were exposed to, those spores may irritate your airways.

Research from the Institute of Medicine links indoor mold exposure with cough, wheezing and upper respiratory symptoms, even in otherwise healthy people. For people with asthma, mold exposure can make symptoms worse.

Not everyone reacts the same way. Some people live with mold in their environment for years with no noticeable side effects. Others develop symptoms quickly. The difference usually depends on a person’s immune system, genetic predisposition to allergies and the total amount of mold spores inhaled over time.

Mold Allergy Symptoms

Mold is a common indoor allergen. If you are sensitive to mold, breathing in mold spores or touching mold can cause an allergic reaction. Your body may react the same way it does to pollen, dust or other allergens.

Mold allergy symptoms can last for weeks or return after repeated exposure. Common mold allergy symptoms include:

Coughing or throat irritation
Itchy, red or watery eyes
Nasal congestion, runny nose or postnasal drip
Skin rash or itching
Sneezing
Wheezing or shortness of breath in people with asthma

If symptoms are usually worse at home, especially in certain rooms like a basement or bathroom, but improve when you are away, you should determine whether there is mold.

“One of the patterns we see in some allergy patients is that their symptoms never fully go away, no matter what medication they are on. When someone describes symptoms that are always worse at home and better on vacation or when they travel, we start asking about their indoor environment. Mold is often part of that answer.”

Alan J. Schecter, MD, Pulmonologist at Catholic Health

Mold and Respiratory Conditions

Asthma

Mold can make asthma worse. If you have asthma and breathe in mold spores, you may have symptoms more often or have more severe asthma attacks. The Centers for Disease Control and Prevention (CDC) also notes that some people who work in moldy places can develop work-related asthma. In some cases, their symptoms do not improve until they are away from the mold exposure.

Children may face a higher risk. Some research links mold exposure early in life with a higher chance of asthma in children who already have a genetic risk. That is why it is important to fix leaks, reduce moisture and remove mold in homes with young children.

Catholic Health provides classes to teach children and adults how to manage asthma and prevent asthma attacks. Learn more.

Hypersensitivity Pneumonitis

Heavy mold exposure over a prolonged period of time can sometimes lead to a serious lung condition called hypersensitivity pneumonitis. This happens when the immune system reacts to mold spores, causing lung irritation and inflammation. This condition is more common in people who work around moldy grain, hay or other damp materials.

Respiratory Infections

Mold-related lung infections are uncommon in healthy people. But they can be serious for people with weakened immune systems, chronic lung disease or conditions such as chronic obstructive pulmonary disease (COPD). If you have a condition that affects your immune system or lungs, talk to your physician before you clean mold or spend time in an area with heavy mold.

What About Black Mold?

Many people worry most about black mold. That concern makes sense, but the color of mold does not tell you how risky it is. Black mold can cause symptoms like other indoor molds, such as allergy or asthma symptoms. But the CDC says there is not enough evidence to show that black mold causes unique or more severe health effects.

The next step is the same for any indoor mold — find the moisture source, fix it and remove the mold.

The CDC does not recommend routine mold tests. In most cases, test results do not change what you need to do. If you see or smell mold, identify the source. Fix the leak or moisture problem, then remove the mold safely.

Who Is Most at Risk

Mold can affect anyone, but some people have a higher risk. People at a higher risk include:

People with mold allergies or other environmental allergies
People with asthma or COPD
Infants and young children
Older adults
People with weakened immune systems, such as those who have cancer, an organ transplant or HIV

If someone in your home is in one of these groups and you think mold may be present, fix the moisture problem right away.

Tips to Prevent Mold Growth in Your Home

Mold needs moisture to grow. The best way to prevent it is to keep your home dry. The U.S. Environmental Protection Agency recommends keeping indoor humidity between 30 and 50%. To reduce mold risk:

Keep Humidity Under Control

Use a dehumidifier in damp areas, such as basements. A small humidity meter can help you check levels.

Use Vents and Fans

Run exhaust fans in bathrooms, kitchens and laundry areas. Make sure dryers and fans vent outdoors. If you don’t have a fan, opening a window for several minutes after showering makes a meaningful difference.

Fix Leaks Fast

Repair roof, pipe or window leaks as soon as possible. Mold can grow on wet materials within 24 to 48 hours.

Dry Wet Areas Right Away

After a flood or major leak, remove wet carpet, drywall or insulation if it cannot dry fully. People with lung disease or weak immune systems should avoid cleanup.

Reduce Condensation

Insulate cold pipes, windows and exterior walls to help stop moisture from collecting on cold surfaces.

When to See a Physician

See a physician if allergy or breathing symptoms do not improve with standard treatment, worsen at home, or start after water damage. People with asthma, chronic lung disease or weakened immune systems should seek care for any new or worsening breathing problems.

“We see patients who have been managing what they thought was chronic sinusitis or recurrent bronchitis for years,” said Dr. Schecter. “When we ask about their home environment, water damage often comes up. Treating the symptoms and fixing the source both matter and help people feel better.”

If you are experiencing persistent respiratory symptoms, allergy symptoms that do not improve, or breathing difficulties that may be related to mold exposure, a Catholic Health physician can help evaluate your symptoms and recommend the right next steps.

Find Care at Catholic Health

Find a Catholic Health doctor near you. Or call 866-MY-LI-DOC (866-695-4362).

June 30, 2026

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