What Causes Asthma?

We don't know what causes asthma. But we do know that:

• Asthma and allergies are likely to run in families and may be inherited.

• Children who have allergies at a young age may be at greater risk for developing asthma as adults.

• Some adults with asthma also had asthma as teenagers and as children. In some individuals, the condition may become less severe over time, but in others, the reappearance of symptoms in adulthood occurs. A respiratory infection sometimes sets it off, but often there is no apparent reason for the reoccurrence or increase in symptoms.

  For more information about asthma in children, go to Asthma In Children.

Certain conditions seem to make asthma worse. And for some it seems to be worse on certain days and at different times of the year. Asthma symptoms occur when sensitive lungs overreact to certain factors called triggers . These irritating factors are part of the environment in which we live and are different for different people.

• Allergies are a common asthma trigger.

• Other asthma triggers range from dust to air pollution, from exercise to weather changes.