Causes of asthma
Inflammation is an important cause of asthma symptoms. Inflammation occurs when tissue is somehow damaged. The damage can occur through an infection, chemically (inhalation of irritating substances), through an allergic reaction etc. The inflammation causes several substances (mediators) to be released from special cells (mast cells) in the airways. These substances cause:
the muscles surrounding the airways to constrict
...the lining of the airways to swell
...the mucus production in the airways to increase.
The breathing difficulties in asthma are thus caused by the reduced diameter of the air passages as a result of a contraction (cramp) in the muscles surrounding the airways. To this can be added the swelling of the airway linings and an increased mucus production also stealing space in the air passages making it further difficult for the air to pass.
