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Mold is a type of fungus that grows in many places in and outside your home. It reproduces by creating spores. These spores float through the air and grow into mold when they come into contact with damp surfaces.

We breathe in mold spores every day. Usually, these spores don’t cause health problems, but people with respiratory disease or weakened immune systems are at an elevated risk of developing breathing issues.

Some molds can trigger an allergic reaction or cause an infection in your lungs. For example, researchers estimate that as many as 2.5 percent of people globally with asthma develop an allergic reaction to molds in the Aspergillus genus.

Keep reading as we look at the typical symptoms of mold in your lungs, how it’s diagnosed, and what the potential treatment options are.

We constantly breathe in mold spores even when we’re outside. Sometimes, these spores can lead to allergic reactions or infections, especially in people with respiratory disease or compromised immune systems.

The fungus Aspergillus fumigatus is responsible for the vast majority of health problems. It grows in many places including decaying vegetation and leaves. Infection or an allergic reaction to this mold is called aspergillosis.

Some other types of molds can also enter your lungs and cause health problems. Infections caused by other molds are called non-Aspergillus infections.

Non-Aspergillus molds are responsible for about 10 to 25 percent of infections in people with blood cancer or receiving organ transplants.

Mold is a large group of fungi found almost anywhere you can find moisture and oxygen. It spreads through tiny spores that waft through the air.

These spores are too small to see with your naked eye. Even the largest spores are usually smaller than 4 ten-thousandths of an inch across.

These spores grow when they encounter moist environments such as vegetation, decaying organic material, or damp wood.

Most health issues caused by mold in the lungs are linked to molds in the Aspergillus genus. But some other types of molds have been reported to caused issues in humans.

Outbreaks of some of these molds have been linked to natural disasters such as tornados and contaminated medical equipment.


Mucormycetes are the most common cause of non-Aspergillus mold infection in humans. The prevalence of Mucormycete infection varies based on geographic region, but an elevated number of cases have been reported in some countries such as France or Switzerland.


Hyalohyphomycetes look similar to Aspergillus molds under a microscope. They’re found in many places such as soil, plant material, and water. In the United States and Europe, a type of Hyalohyphomycete called Fusarium is the second most common cause of non-Aspergillus infection in humans.


Phaeohyphomycetes are a group of more than 100 fungi that have a dark pigmentation. They most often cause mild infection in people with suppressed immune systems. They can cause serious infections in rare circumstances.

Your symptoms can vary depending on what type of mold is in your lungs and what type of reaction you have.

Mold in your lungs can cause an allergic reaction called allergic bronchopulmonary aspergillosis (ABPA).

Symptoms are similar to asthma symptoms and include:

Invasive aspergillosis is when an Aspergillus fungus grows in your lungs. It can cause symptoms such as:

  • fever
  • chest pain
  • cough
  • coughing up blood
  • shortness of breath
  • potentially life threatening symptoms if it spreads past your lungs

Symptoms of non-Aspergillus molds infections tend to be similar.

It’s also possible for mold to form a ball in your lungs. This condition is called aspergilloma when caused by an Aspergillus mold. The ball most often stays in your lungs but can lead to tissue damage.

Symptoms commonly include shortness of breath, cough, or coughing up blood.

Your doctor will ask you about your symptoms and examine your medical history. They may suspect ABPA or a mold infection if you have a condition that weakens your immune system or an existing respiratory condition.

The next step of diagnosis often involves taking a small sample of your lung fluid to examine under a microscope. They take the sample by inserting a special instrument into your nose or mouth to collect a small amount of lung tissue.

Your doctor may also run a blood test to look for evidence of fungal spores or antibodies in your blood.

An X-ray or CT scan may help them rule out other conditions and look for a buildup of mold in your lungs.

It’s almost impossible to avoid all contact with fungal spores, so treatment for mold in your lungs often consists of taking medications.

Corticosteroids often help open your airways to make coughing easier. You may need to take them when daily or only when your symptoms flare.

You may also be given an antifungal medication such as itraconazole, but its effectiveness is still debated.

In a 2014 study, researchers found that 97.1 percent of patients with ABPA received a prescription for oral corticosteroids. About 41 percent of patients received a prescription for oral corticosteroids combined with inhaled corticosteroids and antifungal drugs.

Surgery may be needed if mold reaches your heart or other organs.

The people at the highest risk for developing health complications from breathing in mold are:

What to do if you find mold in your home

You can often remove mold yourself with commercial products, soap and water, or 8 ounces of bleach diluted in a gallon of water. It’s important to wear safety equipment while cleaning mold to avoid breathing it in or getting it on your skin.

When cleaning mold at home:

  • Open a window.
  • Wear a protective mask and gloves and eyewear.
  • Never mix cleaners or ammonia with bleach, and try to avoid mixing chemicals in general.

Call a professional if:

  • there’s a lot of mold or you can’t reach it
  • you have a lot of water damage
  • you have respiratory issues or a known mold allergy
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The outlook for people with ABPA is good if you have only mild symptoms, and it usually heals with treatment. Patients who delay treatment may develop corticosteroid resistance and may need to take corticosteroids long-term.

The outlook for patients with an invasive Aspergillus infection is poor, especially in people with a compromised immune system. The mortality rate in people with immunosuppression or who have undergone an organ transplant is more than 50 percent.

Mold spores are in the air all around us, and we breathe them in almost every day. Most of the time, these spores don’t cause any health issues, but sometimes they can lead to infections or allergic reactions.

People with respiratory conditions like asthma or who have suppressed immune systems are at the highest risk of developing health problems after breathing in mold.

If you think you may be having an allergic reaction to mold, you can visit your doctor. If your doctor confirms that mold is the cause of your symptoms, they’ll likely give you a type of medication called a corticosteroid and possibly an antifungal drug.