Asthma is an inflammatory disorder of the airways, characterized by periodic attacks of shortness of breath, chest tightness, and coughing.
During an asthma attack, the muscles of the bronchial tree become tight and the lining of the air passages swells. It reduces airflow and produces the characteristic wheezing sound. Mucus production is increased.
Most people with asthma have periodic wheezing attacks which can last minutes to days. It can be dangerous if the airflow becomes severely restricted.
In certain cases, asthma symptoms can be triggered by inhaled allergens (allergy triggers), such as pet dander, dust mites, cockroach allergens, molds, or pollens. It can also be triggered by respiratory infections, exercise, cold air, tobacco smoke and other pollutants, stress, food, or drug allergies.
Asthma is found in 3-5% of adults and 7-10% of children. Half of the people with asthma develop it before age 10, and most develop it before age 30. Asthma symptoms can decrease over time, especially in children.
Many people with asthma have an individual and/or family history of allergies, such as hay fever (allergic rhinitis) or eczema. Others have no history of allergies or evidence of allergic problems.