Illness and stress may precipitate an attack. In an asthmatic person's lungs, the airways, called bronchioles, constrict abnormally when stimulated by things such as allergens and exercise, which makes it difficult to expel air from the lungs. Research has linked the presence of allergies with asthma, but not all people with allergies have asthma and not all asthmatics have allergies. Some symptoms are a phlegm or mucus producing cough, wheezing, breathlessness, and the inability to exhale properly. Inflamation of the lungs is present in most cases and can lead to other problems such as respiratory infections.
Genetic susceptibility seems to be one of the major causes of asthma.
However, there are identifiable triggers of the condition. Asthma may be brought on by allergic responses, bacterial and viral infections, exercise, stress, hormones, and other triggers. Thirty to forty percent of women experience a fluctuation in their asthma symptoms during their menstrual cycles.