Asthma affects people of all ages. Some people get asthma when they are young; others when they are older. The causes are not fully understood, although people with asthma often have a family history of asthma, eczema and hayfever (allergic rhinitis). There is some evidence that exposure to environmental factors such as workplace chemicals or tobacco smoke can lead to asthma.

The changes in the lungs involve inflammation of the airways with the secretion of mucous and tightening of the muscles around the airway all of which cause reduced airflow within the bronchi ( tubes that carry the air in the lungs ).
Treatment targets the inflammation and relaxes the muscles allowing more air to enter the lungs.