Asthma is a chronic respiratory problem due to constriction of the respiratory tract causing breathing difficulties in the people involved. These problems are often worsened by physical exercise, cold air, allergens, and some foods.
Chronic inflammation combined with over-reactivity of the respiratory tract results in repeated episodes of wheezing, breathlessness, a sensation of restriction in the chest and coughing, particularly at night or in the early morning.
International recommendations were introduced in 1995 by The Global Initiative for Asthma (GINA) in collaboration with The US National Heart, Lung and Blood Institute and The World Health Organization in order to improve the management of asthma and reduce morbidity. Updated in 2006, these recommendations classify asthma into various grades of severity depending on the patient's clinical features: intermittent asthma, mild persistent asthma, moderate persistent asthma and severe persistent asthma.