Answer:
Step-by-step explanation:
Asthma is characterized by spasmotic contraction of the smooth muscle of the airways, by increased production of an abnormally viscous mucus by bronchial mucous glands, and, in severe attacks, by airway obstruction from mucus that has accumulated in the bronchial tree. This results in a greater or lesser degree of difficulty in breathing. One approach to classifying asthma differentiates cases that occur with an identifiable antigen, in which antigens affect tissue cells sensitized by a specific antibody, and cases that occur without an identifiable antigen or specific antibody. The former condition is known as extrinsic asthma and the latter as intrinsic asthma. Extrinsic asthma commonly manifests first in childhood because the subject inherits an atopic characteristic: the serum contains specific antigens to pollens, mold spores, animal proteins of different kinds, and substances from a variety of insects, particularly cockroaches and mites that occur in house dust. Exacerbation of extrinsic asthma is precipitated by contact with any of the substances to which sensitization has occurred; airway obstruction is often worse in the early hours of the morning. The other form of asthma, intrinsic, may develop at any age, and there may be no evidence of specific antigens. Persons with intrinsic asthma experience attacks of airway obstruction unrelated to seasonal changes, although it seems likely that the airway obstruction may be triggered by infections, which are assumed to be viral in many cases. Asthma attacks may be precipitated by food. For example, in small children, sensitivity to milk may stimulate an attack, and, in some adults, sensitivity to sulfite compounds found in some foods and wine may stimulate an attack. A subgroup of asthmatics are so sensitive to aspirin (acetylsalicylic acid) that ingestion of this chemical may lead to a life-threatening attack.