Asthma

About Asthma

Asthma is a chronic (long-term) lung disease. It affects your airways, the tubes that carry air in and out of your lungs. When you have asthma, your airways can become inflamed and narrowed. This can cause wheezing, coughing, and tightness in your chest. When these symptoms get worse than usual, it is called an asthma attack or flare-up.

The exact cause of asthma is unknown. Genetics and your environment likely play a role in who gets asthma.

An asthma attack can happen when you are exposed to an asthma trigger. An asthma trigger is something that can set off or worsen your asthma symptoms. Different triggers can cause different types of asthma:

• Allergic asthma is caused by allergens. Allergens are substances that cause an allergic reaction. They can include Dust mites
• Mold
• Pets
• Pollen from grass, trees, and weeds
• Waste from pests such as cockroaches and mice

• Breathing in cold air
• Certain medicines
• Household chemicals
• Infections such as colds and the flu
• Outdoor air pollution
• Tobacco smoke

Asthma triggers may be different for each person and can change over time.

Asthma affects people of all ages, but it often starts during childhood. Certain factors can raise your risk of having asthma:

• Being exposed to secondhand smoke when your mother is pregnant with you or when you are a small child
• Being exposed to certain substances at work, such as chemical irritants or industrial dusts
• Genetics and family history. You are more likely to have asthma if one of your parents has it, especially if it's your mother.
• Race or ethnicity. Black and African Americans and Puerto Ricans are at higher risk of asthma than people of other races or ethnicities.
• Having other diseases or conditions such as obesity and allergies
• Often having viral respiratory infections as a young child
• Sex. In children, asthma is more common in boys. In teens and adults, it is more common in women.

The symptoms of asthma include:

• Chest tightness
• Coughing, especially at night or early morning
• Shortness of breath
• Wheezing, which causes a whistling sound when you breathe out

These symptoms can range from mild to severe. You may have them every day or only once in a while.

When you are having an asthma attack, your symptoms get much worse. The attacks may come on gradually or suddenly. Sometimes they can be life-threatening. They are more common in people who have severe asthma. If you are having asthma attacks, you may need a change in your treatment.

Your health care provider may use many tools to diagnose asthma:

• Physical exam
• Medical history
• Lung function tests, including spirometry, to test how well your lungs work
• Tests to measure how your airways react to specific exposures. During this test, you inhale different concentrations of allergens or medicines that may tighten the muscles in your airways. Spirometry is done before and after the test.
• Peak expiratory flow (PEF) tests to measure how fast you can blow air out using maximum effort
• Fractional exhaled nitric oxide (FeNO) tests to measure levels of nitric oxide in your breath when you breathe out. High levels of nitric oxide may mean that your lungs are inflamed.
• Allergy skin or blood tests, if you have a history of allergies. These tests check which allergens cause a reaction from your immune system.

If you have asthma, you will work with your health care provider to create a treatment plan. The plan will include ways to manage your asthma symptoms and prevent asthma attacks. It will include:

• Strategies to avoid triggers. For example, if tobacco smoke is a trigger for you, you should not smoke or allow other people to smoke in your home or car.
• Short-term relief medicines, also called quick-relief medicines. They help prevent symptoms or relieve symptoms during an asthma attack. They include an inhaler to carry with you all the time. It may also include other types of medicines which work quickly to help open your airways.
• Control medicines. You take them every day to help prevent symptoms. They work by reducing airway inflammation and preventing narrowing of the airways.

If you have a severe attack and the short-term relief medicines do not work, you will need emergency care.

Your provider may adjust your treatment until asthma symptoms are controlled.

Sometimes asthma is severe and cannot be controlled with other treatments. If you are an adult with uncontrolled asthma, in some cases your provider might suggest bronchial thermoplasty. This is a procedure that uses heat to shrink the smooth muscle in the lungs. Shrinking the muscle reduces your airway's ability to tighten and allows you to breathe more easily. The procedure has some risks, so it's important to discuss them with your provider.

It sits within Lungs and Breathing and Immune System.

The lead U.S. institute for this subject is the National Heart, Lung, and Blood Institute.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

Medical subject headings

Clinicians and researchers index this subject under Asthma. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for Asthma, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.