ALLERGY

 

INTRODUCTION: An allergy is a hypersensitivity to a particular foreign antigen, called an allergen. Allergens include plant pollens, foods, chemicals in cosmetics, antibiotics such as penicillin, dust, and mold spores. Such allergens are not themselves harmful. Most people, for example, can inhale pollen, eat peanuts, or take penicillin with no ill effects.

HYPERSENSITIVITY: Hypersensitivity means that the immune system overresponds to the allergen, and produces tissue damage by doing so. Allergic responses are characterized by the production of IgE antibodies, which bond to mast cells. Mast cells are specialized connective tissue cells and are numerous in the connective tissue of the skin and mucous membranes.

INFLAMMATORY MEDIATORS: Chemicals in mast cells include histamine and leukotrienes, which are released by the bonding of IgE antibodies or when tissue damage occurs. These chemicals contribute to the process of inflammation by increasing the permeability of capillaries and venules. Tissue fluid collects and more WBCs are brought to the damaged area. In an allergic reaction, the effects of inflammatory chemicals create symptoms such as watery eyes and runny nose (hay fever) or the more serious wheezing and difficult breathing that characterize asthma. Several medications are available to counteract these effects.

ANAPHYLACTIC SHOCK: Anaphylactic shock is an extreme allergic response that may be elicited by exposure to penicillin or insect venoms. On the first exposure, the person becomes highly sensitized to the foreign antigen. On the second exposure, histamine is released from mast cells throughout the body and causes a drastic decrease in blood volume. The resulting drop in blood pressure may be fatal in only a few minutes. People who know they are allergic to bee stings, for example, may obtain a self-contained syringe of epinephrine to carry with them. Epinephrine can delay the progression of anaphylactic shock long enough for the person to seek medical attention.

RELATED;

1.  IMMUNOGLOBULINS  

2.  IMMUNISATION

3.  MEDICAL CONDITIONS

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