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Medically reviewed by Last updated on Mar 23, 2023.

What is asthma?

Harvard Health Publishing

Asthma is a chronic (long-term) lung condition. Air passages narrow and become inflamed. This leads to breathing difficulties and wheezing.

Asthma ranges from mild to severe. Some people have only occasional, mild symptoms. Others have nearly constant symptoms with severe, life-threatening flare-ups.

During an asthma attack, the airways become inflamed. They narrow as the muscles surrounding them constrict. Mucus produced by the inflammation fills the narrowed passageways. As a result, the flow of air is partially or completely blocked.

Asthma affects the lung's larger and smaller airways.

What causes asthma-related inflammation is not clear. But several environmental "triggers" have been identified.Asthma

Many asthma triggers are allergens. Allergens cause the immune system to overreact in some people. Common allergens include:

Also high on the list of asthma triggers are:

For some people with severe asthma, no specific triggers can be identified.

Asthma can develop early, often before age 5. But its symptoms can begin at any age. The condition has a genetic (inherited) component. It often affects people with a family history of allergies.

Symptoms of asthma

Symptoms of asthma include:

For some people with asthma, a chronic cough is the main symptom.

Symptoms of a severe asthma attack can include:

Between asthma attacks or flare-ups, people with mild or moderate asthma may not have any symptoms.

In some people, symptoms flare up only during or after exercise.

People with asthma tend to have more severe symptoms when they have an upper respiratory infection such as a cold or the flu.

Diagnosing asthma

Your doctor will ask about:

These details will help your doctor find ways to help prevent your asthma attacks.

Your doctor also will want to know about:

Your doctor will listen to your back with a stethoscope to detect wheezing.

During an attack, your doctor can assess the severity of your flare-up. He will listen for the amount of airflow in your lungs. He will also observe how you are using your chest muscles to breathe. Blue lips or skin are a sign that you are not getting enough oxygen.

Other tests may be done in the office. These include measuring the speed of the air you can exhale forcibly. This is done with a device called a peak-flow meter.

Another test, called pulse oximetry, measures oxygen levels in your blood. It is done by placing a small plastic clip on the tip of your finger.

During an asthma flare-up, blood tests may be done to check for infection. An arterial blood gas (ABG) test can be done on a blood sample. It provides a more accurate measure of oxygen levels. Your doctor also may want you to have a chest X-ray.

Two tests are commonly used to show how well your lungs are functioning:

During spirometry, you exhale into a device that analyzes the amount and volume of airflow. One part of the test may be repeated after you are given a bronchodilator. This medication relaxes the muscles surrounding the airways. If airflow improves with a bronchodilator, it indicates that you have asthma.

Sometimes a challenge test is done when spirometry appears normal. For this test, you inhale a medication to see if it causes your airway muscles to tighten up. People with asthma are more sensitive to this medication: their airway muscles are more likely to tighten up.

Peak-flow meters often are given to asthma patients for use at home. They can use them to monitor their asthma. These devices help to detect the earliest signs of an asthma flare-up.

Your doctor may want to do a blood test or allergy skin testing. These tests are used to determine specific substances ("allergens") that can trigger an allergy.

Expected duration of asthma

Asthma in adults often is a lifelong condition. With treatment, symptoms can be controlled. They can be infrequent or very mild.

In about half of asthmatic children, the asthma goes away on its own. Or it becomes less severe over time. However, it may reappear later in life.

Asthma episodes can go away on their own or with the help of asthma medications. Attacks vary in frequency and severity. It is often dependent on what triggers the attack.

Preventing asthma

Some asthma episodes can be prevented by avoiding or minimizing exposure to triggers.

These include environmental triggers such as:

If exercise triggers your asthma:

Eliminating allergens at home often can go a long way to control asthma symptoms.

If dust mites are a trigger:

Some people may need to avoid animals entirely. Others may benefit from taking preventive medicine before an anticipated exposure to animals. Pet owners should keep pets out of bedrooms and bathe them regularly.

Those who are affected by pollens should

Prevention also means learning to anticipate future attacks. Monitor your symptoms and peak-flow readings to help identify a coming attack before symptoms develop. This allows you to adjust your medications to prevent an attack.

Early signs or symptoms of an asthma flare-up include:

Treatment options

The following list of medications are related to or used in the treatment of this condition.

View more treatment options

Treating asthma

Treatment focuses on:

If you have chronic asthma, work with your doctor to write an asthma-management plan. The plan specifies:

Several types of medication are available to treat asthma. Some treat acute attacks (the "quick relievers"). Others prevent attacks from happening (the "controllers").

It is important to take preventive asthma medications as prescribed. You should take them even when you are not having symptoms.

Severe asthma attacks must be treated in a hospital. There, oxygen can be administered, and drugs may be given intravenously or with a nebulizer. In life-threatening cases, the patient may need a breathing tube placed in the large airway and artificial ventilation.

When to call a professional

Call your doctor whenever you or your child has persistent:

Some children with asthma may not complain specifically of shortness of breath. However, they may flare their nostrils or use their chest and neck muscles when breathing. These are signs that they are having trouble.

If you already have been diagnosed with asthma, call your doctor if your symptoms:

For example, call your doctor if you must use your rescue bronchodilator more than two or three times a day. Also call if your peak-flow-meter readings are in the yellow or red zones.

If you have an asthma attack and your symptoms persist despite your usual medications, seek emergency help immediately.


Although asthma cannot be cured, it almost always can be controlled successfully. Most people with asthma lead relatively normal lives.

Additional info

American Academy of Allergy, Asthma & Immunology (AAAAI)

American Lung Association

National Institute of Allergy and Infectious Diseases (NIAID)

Learn more about Asthma

Treatment options

Care guides guides (external)

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.