We do not know exactly what causes asthma. Some people are genetically predisposed to asthma, and most are likely to have allergies as well.

A number of environmental factors play a role in developing the condition (eg. contact with allergens, exposure to tobacco smoke, and some types of respiratory infections, especially at an early age.)

Psychological factors may aggravate symptoms of asthma, but do not cause the disease.

At any given moment, about 5 to 10% of the population suffers from asthma.

Asthma is the most common chronic childhood illness and one of the most common chronic adult illnesses. Many studies suggest that asthma and allergies are more widespread today than they were 20 years ago. The cause for this increase is unknown. On the one hand, there is greater awareness of these conditions; but a number of environmental factors must also considered.

For most asthma sufferers, the condition is so mild that regular medication is unnecessary. About one-quarter of asthmatics experience daily symptoms that require regular drugs. The remainder (about 5%) have severe asthma that requires regular high doses of inhaled corticosteroids and, in some cases, may even require oral corticosteroids (taken by mouth).

Asthma can lead to a number of problems: debilitating symptoms preventing the individual from doing activities, visits to the emergency room, hospitalization, and missing time from school or work. Asthma symptoms can affect the sufferer's quality of life and are costly to society. Asthma can also be fatal, although, fortunately, this is extremely rare.

Asthma can change over time.

Adolescents who had childhood asthma often experience a remission; but once you have the illness, it rarely goes away completely. Proper treatment and preventive measures can dramatically reduce symptoms.

Asthma can develop at any age. Asthma that begins after age 40 is generally more severe; and 25% of all asthmatics contract the illness after 40.

In up to 50% of all asthmatics, symptoms disappear before the age of 10. Childhood asthma sufferers are about twice as likely to be boys, but there is a higher percentage of female asthmatics in other age groups.