ALLERGY and ITS TYPES

Allergy is defined as altered reaction to the antigen-antibody interaction in a person who is hypersensitive to an offending substance. Allergy is therefore also called hypersensitivity. A person may be hypersensitive to a variety of substances such as chemicals, dust, pollen-grains, hay, fungal spore, fungal hyphae, mould, fabrics, feathers, fur, plants, bacteria, foods, heat, cold, sunlight etc. A person who is sensitive to any of these, come in contact will produce immediate immunological reactions. The reactions that are adverse are either mediated by humoral antibody or cells. The humoral antibody reactions produces immediate hypersensitivity while the cells produce delayed hypersensitivity. The antigens which produce hypersensitivity are referred to as allergens or sensitizing antigens. 

During allergic reactions, there is increased release of histamine from mast cells. It causes marked dilation of all the peripheral blood vessels and the capillaries become highly permeable so a large amount of fluids leak out from the blood into the tissues. The blood pressure decreases drastically often resulting in the death of the individual within a short time. The exact nature of the substance of which a person is hypersensitive must be known then only he/she can be properly treated. Some forms of allergy are mentioned below:

ü Hay Fever: In this allergic form, there is swollen, reddened, running eyes and nose. The drugs called antihistamines are of major importance in the treatment of this allergic disorder.

ü Asthma: In this case, the tissues surrounding the respiratory tract in the lungs swells up and compress the tracts. Hence, a person feels difficulty in breathing. Antihistamine drugs are given in this disease.

ü Anaphylactic Shock: It is an allergic reaction involving all the tissues of the body and occurs in a few minutes after the injection of an antigen such as penicillin. This type of allergic reactions are very serious. Histamine released from ruptured mast cells causes marked dilation of all the arteries and a large amount fluid passes from the blood to the tissues so there is a drastic fall in blood pressure. The affected person may become unconscious and the individual may die within a short time.

Allergy mostly affects the skin mucous membrane. Hay fever affects the mucous membrane of the nose, eyes and upper respiratory tracts. In asthma, the lower portions of the respiratory system are severely affected. In eczema, the skin becomes red, followed by the appearance of minute blisters. Allergy is a serious immune disorder and it should be handled properly. Prevention is always better than cure so we should always keep ourselves away from the substances which are allergic for us.