Allergies and Hypersensitivities - How allergens affect the body

Allergic symptoms can range from itching eyes, running nose, coughing, difficulty in breathing, and welts on the skin to nausea, cramps, and even going into a state of shock, depending upon the severity of the particular individual's sensitivity and response. Almost any part or system of the body can be affected, and almost anything can pose an allergic threat to somebody.

The Role of Antibodies

The system of an allergic individual reacts to such substances in the way it would react to an invading disease organism: by producing antibodies whose job it is to neutralize the allergen. In the process of fighting off the effects of the allergen, the body's defense mechanism may overreact by dumping a chemical mediator, histamine , indiscriminately into the individual's bloodstream. It is the overabundance of this protective chemical that causes the discomforts associated with allergies.

At the same time, the antibodies can sensitize the individual to the allergen. Then, with each new exposure to the allergen, more antibodies are produced. Eventually the symptoms of allergy are produced whenever the allergen is encountered. Most allergic reactions, including hay fever, asthma, gastrointestinal upsets, and skin rashes, are of the type just described; their effect is more or less immediate. A second type, known as the delayed type, seems to function without the production of antibodies; contact dermatitis is an example of the delayed type.

Eosinophils

Some individuals seem to be sensitive to only one known allergen, but others are sensitive to a variety of substances. Persons who suffer acute allergic reactions have abnormally high levels of a type of white blood cell called eosinophil . The eosinophil contains an enzyme that may have some control over the allergic reaction, and varying degrees of the enzyme's efficiency appear to account for individual differences in the severity of allergic reactions.

Allergic Symptoms in Children

Many of the common allergies appear during the early years of life. It has been estimated that nearly 80 percent of the major allergic problems begin to appear between the ages of 4 and 9. Allergic youngsters may have nasal speech habits, breathe through the mouth, have coughing and wheezing spells, or rub their eyes, nose, and ears because of itching. A not uncommon sign of allergic reaction in a child may be dark circles under the eyes caused by swelling of the mucous membranes to such an extent that blood does not drain properly from the veins under the lower eyelids. Nose twitching and mouth wrinkling also are signs that a youngster has allergic symptoms.