An allergy is an abnormal response of the immune system of the body to some type of foreign substance. The substance that triggers the allergic reaction is called an allergen. Initial contact with the allergen does not produce any symptoms. However, with time the immune system begins to form antibodies to the allergen, and certain types of white cells become sensitized to these same allergens. Future interactions with the allergen may then trigger a response from some of these specialized white cells. The response to these sensitizing allergens varies from mild sneezing to respiratory difficulty, shock, and death.
Causes of Allergic Reaction
The cause of allergic reactions is the repeated exposure to an allergen, or substance that has previously stimulated the immune system. The antibodies which have developed in response to the antigen react with it when the body is exposed again. When further exposure occurs, the complex of antibodies and allergens causes certain white cells, called mast cells, to release histamine. This chemical causes various changes in the blood vessels, the lungs, the skin, etc.
Signs and Symptoms of Allergic Reaction
The symptoms which develop depend in part on how the allergen is presented to the body, whether through respiration, ingestion on inoculation. Allergic rhinitis causes nasal itching and sneezing. Itchy, red eyes develop. Food allergies may cause itching and swelling of the mouth and throat. Nausea, vomiting and diarrhea may develop. Severe reactions can lead to a rash, swelling and shortness of breath. Drug allergies typically cause the rash. Nausea and diarrhea are common. Swelling and wheezing may also occur. Anaphylaxis, the most severe form of allergic reaction, develops when someone is extremely sensitive to a particular allergen. There is a generalized response in the body, with shortness of breath, difficult breathing, decreased blood pressure, rashes, swelling, and possible loss of consciousness. Death may occur.
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Medical Content Last Updated on 07/12/2008
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