The box accompanying a story on asthma (Medical News, Nov. 6) did not distinguish clearly between oral and inhaled steroids as a treatment for asthma. Oral steroids can have serious side effects when used for a long time. The potential side effects of inhaled steroids are much less common and less serious. (Published 11/13/90)

Asthma is a noncontagious disease of the airways in the lungs. Bronchial tubes, which carry air to the sacs of the lungs, become narrowed or blocked, making breathing difficult. There is no cure, but the vast majority of people with asthma can live normal lives by "managing" their disease -- by avoiding or minimizing environmental "triggers" that cause asthma and taking certain medications to help prevent attacks and relieve symptoms.

The Cause. People with asthma are especially sensitive to various "triggers" in the environment. Triggers can include common allergens such as pollen, mold, animal dander, smoke, dust and foods. Exercise, respiratory infections and weather changes also can trigger or worsen an asthma attack.

Bronchial tubes become blocked by swelling of the tube linings, squeezing of the tubes by surrounding muscles, and secretion of mucus, which plugs the airways.

Toll. Asthma strikes 10 million Americans, including 3 million under age 18. It causes:

5,000 deaths a year (at highest risk are adults over 50 and children under 9).

454,000 hospitalizations a year.

15 million doctor visits a year.

Treatment. All asthma drugs have side effects, some serious, and each patient should be closely monitored by a physician. The four main types of medications are:

Cromolyn sodium, an inhaled drug, helps prevent asthma attacks by suppressing inflammation.

Adrenaline-like drugs, called bronchodilators, are taken orally or inhaled and help lessen acute symptoms by opening airways.

Steroids, in tablet or spray form, are sometimes used to relieve severe attacks but are most likely to cause side effects when used for a long time.

Theophylline, a caffeine derivative, opens airways by relaxing muscles surrounding bronchial tubes.