No one knows exactly what causes asthma.

Some people think it’s a combination of genetics (it runs in families) along with environmental exposures and certain infections. Asthma is complex; we don’t necessarily know what causes the disease, but we can usually figure out what affects a person’s day-to-day control.

Over time, people learn what triggers their asthma. Knowing the triggers can help a person avoid or minimize those exposures. 

Secondhand Smoke and Asthma

Secondhand smoke can lead to the development of asthma. Smoke can also trigger asthma in some children.

People who have children with asthma should not smoke anywhere near them.

A newer area of study is third-hand smoke, which is when smoke settles and becomes part of the dust on clothes, furniture, etc. It is possible for someone to live next door to a smoker and be exposed to smoke.