This is a lung disorder that includes periodic attacks of wheezing, alternating with periods of relatively normal breathing. Symptoms of asthma can occur spontaneously or can be triggered by respiratory infections, exercise, cold air, tobacco smoke or other pollutants, stress or anxiety, or by food or drug allergies. The muscles of the bronchial tree become tight and the lining of the air passages become swollen, causing reduced airflow, thus, producing a wheezing sound and increasing mucus production. An asthma attacks can last for a few minutes to days, and can become dangerous if the airflow becomes severely restricted. 

No cause can be demonstrated for Bronchial asthma, it is usually intrinsic; occasionally it is caused by a specific allergy, like that of mold, pollen or dust . Allergy is not necessarily the cause of the asthma, though most individuals with asthma will have some positive allergy tests. Asthma can develop at any age, but some children seem to outgrow theillness. Risk factors include self or family history of eczema, allergies or family history of asthma.

Decreased or controlled exposure to known allergens can help in prevention. Staying away from cigarette smoke, removing animals from bedrooms or entire houses and avoiding foods that cause symptoms, can help.