What is Allergy?
An abnormal response to certain substances, which may cause asthma, hay fever, and other allergic disease. The body may react to the presence of certain materials (allergens), such as animal and plant products, by producing substances called antibodies. When the same material enters the body a second time, a reaction ensues between this substances and the antibodies.
When the reaction occurs in the skin, the escape of fluid and the contraction of the smooth muscles around the hair follicles produce the swellings seen in hives. When it occurs in the nose, collections of fluid in the mucous membranes cause the familiar symptoms of hay fever. An allergic reaction in the air passages (the bronchioles) produces asthma, and such a reaction in the intestines results in cramps and diarrhea.
4 Ways in which Allergens Enter The Human Body
Such substances include the wind-carried pollens of ragweeds, grasses, and trees. Also the seeds of molds that grow on grains, insect dust, the dandruff of dogs or horses, and house dust. These irritants may affect the nose, causing sneezing, discharges, and blocking of the nasal passages. If the allergy is caused by seasonal allergens, such as pollen, molds, and insect dust, it's called hay fever.
If the irritant is present throughout the year, the allergy is termed perennial allergic rhinitis. Allergic asthma is a more serious ailment. It develops when the air passages are sensitive to the airborne allergens. The allergic reaction causes a spasm of the muscles of the bronchioles and stimulates the production of thick mucus. The consequent narrowing and blocking of the air passages make breathing difficult. Although most cases asthma are allergic in nature, some may be caused by infection or heart disease. In many instances the cause is unknown.
Skin Contact with Allergens
An allergic skin inflammation (contact dermatitis) can be caused by contact with a number of substances. These include plants (poison ivy, poison oak, primrose, ragweed), dyes (used on fur and clothing), metals (mercury in antiseptics, and nickel-containing jewelry), nail polish, penicillin, sulfa drugs, and plastics.
Foods and Drugs
Almost any type of allergy can be produced by food. These type include asthma, skin conditions (hives and eczema), gastrointestinal complaints involving cramps, stomach gas, nausea, vomiting, and diarrhea.
Drugs are also frequent source of allergy. Some types of anemia (deficiency of red blood cells), leukopenia (deficiency of white blood cells), or thrombocytopenia (deficiency of blood platelets) may caused by drug allergy. Injected drugs are more likely to produce an allergy than those taken by mouth. Serum sickness is an allergic that occasionally follows the injection of penicillin or serum prepared from animals. The reaction usually develops several days after the injection. It consists of hives, giant swellings, inflammation of the joints, and fever.
Allergic reactions from the stings of bees, wasps, and hornets are common. The oldest recorded case of this type is found in the hieroglypic account on the tomb of King Menes of Egypt, which tells of his death from the sting of a hornet in 2641 BC.
- Samuel M. Feinberg, M.D., Living with Your Allergy (1958)
- Encyclopedia International by Samuel M. Feinberg, M.D., Director, Allergy Research Laboratory, Evanston Hospital, Evanston, Illinois; Professor Emeritus of Medicine, Northwestern University. Author, Allergy in Practice; Living with Your Allergy.