Asthma

Asthma is a pathological condition of the respiratory system caused by narrowing of the ducts leading to the lungs, making breathing more difficult. Patients with asthma usually have a combination of lung problems: spasm of the smooth muscle fibers of the bronchi (bronchospasm), swelling of the mucous membranes, and increased mucus production. Asthma can be caused by allergic reactions to food or inhaled allergens, cold air, cigarette smoke, exercise, and stress. Respiratory infections can also contribute to asthma.