Jodi Roberts, age 10, of Nashua, N.H., for her question:` ,S'~

WHAT CAUSES ASTHMA?

Asthma is a disease that makes breathing difficult. Attacks are caused by a partial blocking of the small bronchial tubes in the lungs. This blocking results from spasms or contractions of the bronchial muscles, swelling of the mucous membranes that line these muscles and production of phlegm.

The most common type of asthma, allergic bronchial asthma, is caused by a specific allergic reaction. A narrowing of the lung airways results.

In most cases of allergic bronchial asthma, the allergy is caused by ordinary substances such as house dust, airborne pollens or certain foods.

Asthma is also often associated with hay fever, which is also an allergy.

Sometimes attacks of asthma can follow periods of heavy exertion or emotional strain. Also, an infection of the nose and throat can hasten the start of an attack.

A sudden change in the weather also may bring on an attack. With some patients, attacks of asthma may occur seasonally if the air contains specific harmful elements.

An asthmatic attack often comes on suddenly. Symptoms include a wheezing or whistling sound from the chest when the patient inhales and even greater wheezing when he exhales. The patient often may gasp for air and feel that he is suffocating.

Doctors often prescribe one of a number of different drugs as a treatment for asthma. Popular ones include Adrenalin, which is also called epinephrine; aminophylline; and ephredrine. All of these help to relieve the symptoms of asthma.

Other drugs, including ACTH and cortisone, sometimes prove to be necessary in some cases of asthma.

Adrenalin is a registered trade name. Doctors report that it relaxes the muscles in the bronchi, which are the large air passages into the lungs.

In the treatment of some asthma cases, the doctor may hyposensitize the patient to the substances that cause his asthma attacks. This treatment involves small injections at regular intervals of a preparation made from the substances to which the person is allergic.

The doctor gradually increases the strength of the injections until the patient's body has built up resistance to the substance.

When an attack of asthma starts, the patient often complains of a feeling of tightness in the chest. He has a hacking cough and shortness of breath. Thick mucus called phlegm develops in the patient's lungs and the cough becomes more intense. The patient may feel a bit better temporarily after he has coughed up some of the phlegm.

When doctors report that an attack of asthma is caused by the emotional stress and frustration common to modern society, they do not consider these actually to be causes of the disease but rather factors that reduce the patient's resistance or increase his sensitivity to the allergens to which he reacts.

Many children are among the millions of people who suffer from asthma all over the world.