MODEL RELEASED. Using asthma inhaler. Doctor instructing a boy on how to use an asthma inhaler. Asthma is a condition in which the small airways (bronchioles) in the lungs constrict, making it difficult to breathe. This causes wheezing, coughing and breathlessness. The inhaler is an aerosol pump, which releases bronchodilator drugs that widen the airways. Asthma attacks can be brought on by exercise, allergic reactions and cold weather. Asthma usually develops during childhood, and generally improves as the patient matures.