Asthma is a condition in which the airways narrow—usually reversibly—in response to certain stimuli.

  • Coughing, wheezing, and shortness of breath that occur in response to specific triggers are the most common symptoms.
  • Doctors confirm the diagnosis of asthma by doing breathing (pulmonary function) tests.
  • To prevent attacks, people should avoid substances that trigger asthma and should take drugs that help keep airways open.
  • During an asthma attack, people need to take a drug that quickly opens the airways.

Asthma affects more than 25 million people in the United States, and it is becoming more common. The reason for the increase in asthma is not known.


Although asthma is one of the most common chronic diseases of childhood, adults can also develop asthma, even at an old age. Asthma affects more than 6 million children in the United States and occurs more frequently in boys before puberty and in girls after puberty. Asthma can eventually resolve in children. However, sometimes asthma that appears to resolve recurs years later.

The most important characteristic of asthma is narrowing of the airways that can be reversed. The airways of the lungs (the bronchi) are basically tubes with muscular walls. Cells lining the bronchi have microscopic structures, called receptors. These receptors sense the presence of specific substances and stimulate the underlying muscles to contract or relax, thus altering the flow of air. There are many types of receptors, but two main types of receptors are important in asthma:

  • Beta-adrenergic receptors respond to chemicals such as epinephrine and make the muscles relax, thereby widening (dilating) the airways and increasing airflow.
  • Cholinergic receptors respond to a chemical called acetylcholine and make the muscles contract, thereby decreasing airflow.


(See also Drugs for Preventing and Treating Asthma.)

  • Drugs to reduce inflammation
  • Drugs to widen the airways

An array of drugs can be used to prevent and treat asthma in adults or in children (see also Asthma in Children : Treatment of Asthma). Doctors may use the term “rescue treatment” to describe treatment of an acute attack and “maintenance treatment” to describe treatments aimed at preventing attacks. Most of the drugs used to prevent asthma attacks are also used to treat an asthma attack but in higher doses or in different forms. Some people need to use more than one drug to prevent and treat their symptoms. The Drugs for Preventing and Treating Asthma are discussed in more detail elsewhere.

Therapy is based on two classes of drugs:

  • Anti-inflammatory drugs
  • Bronchodilators

Anti-inflammatory drugs

Anti-inflammatory drugs suppress the inflammation that narrows the airways. Anti-inflammatory drugs include corticosteroids (which can be inhaled, taken by mouth, or given intravenously), leukotriene modifiers, and mast cell stabilizers.


Bronchodilators help to relax and widen (dilate) the airways. Bronchodilators include beta-adrenergic drugs (both those for quick relief of symptoms and those for long-term control), anticholinergics, and methylxanthines.


Immunomodulators, drugs that directly alter the immune system are sometimes used for people with severe asthma, but most people do not need immunomodulators. These drugs block substances in the body that cause inflammation.


Education about how to prevent and treat asthma attacks is beneficial for all people who have asthma and often for their family members. Proper use of inhalers is essential for effective treatment. People should know

  • What can trigger an attack
  • What helps to prevent an attack
  • How to use drugs properly
  • When to seek medical care