What are the causes for Asthma Medications?

Asthma is caused by chronic (ongoing, long-term) inflammation of these airways passages. Individuals with asthma are highly sensitive to various "triggers" that lead to inflammation of the airways. When the inflammation is triggered by one or more of these factors, the air passages swell and fill with mucus. The muscles within the breathing passages contract and narrow (bronchospasm). The narrow airways make it hard to exhale (breathe out from the lungs).

Source: http://www.emedicinehealth.com