What is asthma?

Asthma is a chronic disease that affects the airways of the lungs. During normal breathing, the bands of muscle that surround the airways are relaxed and air moves freely. During an asthma episode or "attack," there are three main changes that stop air from moving easily through the airways:

  • The bands of muscle that surround the airways tighten and make the airways narrow. This tightening is called bronchospasm.
  • The lining of the airways becomes swollen or inflamed.
  • The cells that line the airways produce more mucus, which is thicker than normal and clogs the airways.

These three factors - bronchospasm, inflammation, and mucus production - cause symptoms such as difficulty breathing, wheezing, and coughing.

Who is affected by asthma?

Asthma affects 22 million Americans; about 6 million of these are children under age 18. People who have a family history of asthma have an increased risk of developing the disease. Asthma is also more common in people who have allergies or who are exposed to tobacco smoke. However, anyone can develop asthma at any time. Some people may have asthma all of their lives, while others may develop it as adults.

Symptoms and Causes

What causes asthma?

The airways in a person with asthma are very sensitive and react to many things, or "triggers." Asthma “triggers” are those things that make the airways tighten and become inflamed. Contact with these triggers causes asthma symptoms. Sometimes a trigger brings on a reaction right away, but other times it may take several hours or days before symptoms begin. One of the most important parts of asthma control is to identify your triggers and then avoid them when possible. The only trigger you do not want to avoid is exercise. Pre-treatment with medicines before exercise can allow you to stay active yet avoid asthma symptoms.

What are the most common asthma triggers?

There are many kinds of triggers. The most common asthma triggers are:

  • Infections: colds, viruses, sinus infections, flu
  • Weather: cold air or changes in temperature and humidity
  • Allergens: outdoor - pollens (trees, grasses, ragweed and weeds); mold spores ; indoor: molds, animal dander, dust mites, cockroaches
  • Exercise
  • Tobacco smoke
  • Irritants (strong odors from perfumes, cleaning agents, wood smoke, air pollution, etc.)
  • Strong emotions such as anxiety, or episodes of crying, yelling, or laughing hard
  • Certain medications
  • Food allergies (not a common trigger in adults, but can cause asthma symptoms, usually in children under age 5)

Some people are affected by a number of triggers, while others may only have one trigger such as in exercise-induced asthma. It is important to recognize your triggers and avoid them, if possible.

For those triggers you cannot avoid, there are steps you can take to limit your contact and treat your asthma before you encounter them. This is an important step in controlling asthma.

The only trigger you do not want to avoid is exercise. If your asthma is well-controlled, you should be able to participate in any activity you want to do.

What are the symptoms of asthma?

People with asthma have symptoms when the airways are narrowed (bronchospasm), swollen (inflamed), or filled with mucus. Common symptoms of asthma include:

  • Coughing, especially at night
  • Wheezing
  • Shortness of breath
  • Chest tightness, pain, or pressure

Not every person with asthma has the same symptoms in the same way. You might not have all of these symptoms, or you might have different symptoms at different times. The symptoms might also vary from one asthma episode to the next, being mild during one and severe during another.

Some people with asthma might have extended symptom-free periods, interrupted by periodic asthma episodes, while others have some symptoms every day. In addition, some people with asthma might only have symptoms during exercise, or when they are exposed to allergens or viral respiratory tract infections.

Mild asthma episodes are generally more common. Usually with treatment, the airways open up within a short time period. Severe episodes are less common, but last longer and require immediate medical help. It is important to recognize and treat even mild symptoms to help prevent severe episodes and keep asthma in better control.

What are the early warning signs of asthma?

Early warning signs are changes that happen just before or at the very beginning of an asthma episode. These changes start before the well-known symptoms of asthma and are the earliest signs that a person's asthma may be worsening.

In general, these signs are not severe enough to stop a person from going about his or her daily activities. By recognizing these signs, you can stop an asthma episode or prevent one from getting worse. Early warning signs include:

  • Frequent cough, especially at night
  • Losing your breath easily or shortness of breath
  • Feeling very tired or weak when exercising
  • Wheezing or coughing during or after exercise
  • Decreases or changes in a peak expiratory flow
  • Signs of a cold, upper respiratory infection, or allergies (sneezing, runny nose, cough, congestion, sore throat, and headache)
  • Trouble sleeping

If you have early warning signs or symptoms, you should follow the steps listed in your Asthma Action Plan. If you do not have one, you should notify your provider.

What are the symptoms of worsening asthma?

If early warning signs and symptoms are not recognized and treated, the asthma episode can progress and symptoms might worsen. As symptoms worsen, you might have more difficulty performing daily activities and sleeping. Symptoms of worsening asthma include:

  • A cough that won't go away (day and night)
  • Wheezing
  • Tightness in the chest
  • Shortness of breath
  • Poor response to quick relief, inhaled medicines (bronchodilators)

What are the late, severe symptoms of asthma?

When asthma symptoms become severe, you will be unable to perform regular activities. If you have late, severe symptoms, follow the "Red Zone" or emergency instructions in the Asthma Action Plan immediately. These symptoms occur in life-threatening asthma episodes. You need medical help right away.

Late, severe symptoms include:

  • Severe wheezing (both when breathing in and out)
  • Coughing that won't stop
  • Very rapid breathing
  • Inability to catch your breath
  • Chest pain or pressure
  • Difficulty talking
  • Inability to fully exhale
  • Feelings of anxiety or panic
  • Pale, sweaty face
  • Blue lips or fingernails

Diagnosis and Tests

How is asthma diagnosed?

To diagnose asthma, your doctor will first review your medical history, family history, and symptoms. Your doctor will want to know any past history of breathing problems you may have had, as well as a family history of asthma, allergies, eczema (a bumpy, itchy skin rash caused by allergies), or other lung disease. It is important that you describe your symptoms in detail (cough, wheeze, shortness of breath, chest tightness), including when and how often they occur.

The doctor will perform a physical examination and listen to your heart and lungs. He or she may also order breathing tests, allergy tests, blood tests, and chest and sinus X-rays. The tests will find out if you do have asthma and if there are any other conditions that are contributing factors.

Management and Treatment

How is asthma treated?

Asthma can be controlled, but not cured. It is not normal to have frequent symptoms, trouble sleeping, or trouble completing tasks. Appropriate asthma care will prevent symptoms and visits to the emergency room and hospital. Asthma medicines are one of the mainstays of asthma treatment. The drugs used to treat asthma are explained below.

Anti-inflammatories: These are the most important drugs for most people with asthma. Anti-inflammatory drugs reduce swelling and mucus production in the airways. As a result, airways are less sensitive and less likely to react to triggers. These medications need to be taken daily and may need to be taken for several weeks before they begin to control asthma. Anti-inflammatory medicines lead to fewer symptoms, better airflow, less sensitive airways, less airway damage, and fewer asthma attacks. If taken every day, they CONTROL or prevent asthma symptoms.

Bronchodilators: These drugs relax the muscle bands that tighten around the airways. This action opens the airways, letting more air in and out of the lungs and improving breathing. Bronchodilators also help clear mucus from the lungs. As the airways open, the mucus moves more freely and can be coughed out more easily. In short-acting forms, bronchodilators RELIEVE or stop asthma symptoms by quickly opening the airways and are very helpful during an asthma episode. In long-acting forms, bronchodilators provide CONTROL of asthma symptoms and prevent asthma episodes.

Asthma drugs can be taken in a variety of ways. Inhaling the medications - by using a metered dose inhaler, dry powder inhaler, or nebulizer - is one way of taking asthma medicines. Oral medicines (pills or liquids you swallow) may also be prescribed.

Asthma severity

Asthma is classified as either "intermittent" (comes and goes) or "persistent" (lasting). Persistent asthma is further described as being mild, moderate, or severe. The severity of asthma is based on how often you have symptoms both during the day and night, as well as by the results of lung function tests and by how well you can perform activities. The "severity" of asthma refers to how "intense" or "strong" your asthma is.

Asthma control

Asthma control is the goal of asthma treatment. Regardless of your asthma severity, it may or may not be controlled. Asthma control means:

  • You are able to do everything you want to do at work and home
  • You have no (or minimal) asthma symptoms
  • You do not wake up from your sleep or earlier than usual in the morning due to asthma
  • You rarely need to use your reliever medicine (inhaler)

Another major part of your treatment is that you are happy with your asthma care and believe your asthma is controlled.

Monitoring symptoms

A key part of treatment is keeping track of how well your lungs are working. Monitoring your symptoms - what they are, how and when they happen, and how severe they are - is an important part of being able to control your asthma.

Sometimes asthma is monitored using a peak flow meter. A peak flow (PF) meter measures how fast the air comes out of your lungs. It can help you know when your asthma is getting worse, sometimes even before you have symptoms. By taking daily peak flow readings, you can learn when to adjust medications to keep asthma under good control. It is also used to create your asthma action plan (see below). Your doctor can use your peak flow readings to adjust your treatment plan in some cases.

Outlook / Prognosis

What is the outlook for someone with asthma?

By learning about asthma and how it can be controlled, you take an important step toward managing this disease. Work closely with your asthma care team to learn all you can about your asthma, how to avoid triggers, what your medications do, and how to take them correctly. With proper care, you can live free of asthma symptoms and maintain a normal, healthy lifestyle.

Living With

What is an asthma action plan?

Asthma Action Plan

Based on your history and asthma severity, you and your doctor will develop a care plan called an “asthma action plan.” The asthma action plan describes when and how to use your medicines, actions to take when asthma worsens, and when to seek emergency care. Make sure you understand this plan. If you do not, ask your asthma care provider any questions you may have.

Your asthma action plan is one of the keys to controlling asthma. Keep it readily available to remind you of what you need to do every day to control asthma and what you need to do when symptoms occur.

Goals of asthma therapy

These are the goals of asthma treatment:

  • Live an active, normal life
  • Prevent chronic and troublesome symptoms
  • Attend work or school every day
  • Perform daily activities without difficulty
  • Stop urgent visits to the doctor, emergency department, or hospital
  • Use and adjust medications to control asthma with few or no side effects

If you are unable to reach all of these goals, your asthma is not under control. You should contact your asthma care provider for advice.


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Last reviewed by a Cleveland Clinic medical professional on 06/08/2017.


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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy