Allos = Altered
Ergos = Reaction
Coined by Von Pirquet,1906
IS an altered response OF immune system TO a subsequent encounter WITH the foreign substance TO which body has already been sensitized due to previous exposure.
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In layman's language ALLERGY IS UNTOWARD REACTION OF THE BODY TO ANY SUBSTANCE. So such reaction is not expected in majority of individuals Let us have some example. Somebody is moving around & an honeybee gives a sting over forearm. What happens? Some pain, some swelling, some burning at local site for few minutes and He / She forgets about it within a short period. But in certain individuals, with similar sting These pain, swelling & redness at the local site-goes on increasing. Swelling also occurs over face, lips, all parts of body with redness & itching, there is red fluffy face within no time. Pulse rate is increased and individual has difficulty in breathing. All this occurs within seconds or minutes and if not treated immediately individual may succumb--It is Anaphylaxis The most severe form of allergic reaction. Allergic Rhinitis Nose Blocked Sneezing Doctor, Skin Allergy in Rajasthan
Luckily it is uncommon, majority of allergic reactions are mild & common - every third individual is suffering from some allergy. Commonest is ALLERGIC RHINITIS-bouts of sneezing, with watering from nose, Itching in nose or palate with red & watery eyes.
Other Common examples of allergy are Asthma, Urticaria, Conjunctivitis, Pharyngitis, Bronchitis, Dermatitis, Food Allergy & Drug Allergy.