Allergy

Abstract

Allergy is immunity gone wrong. Different people are allergic to a wide range of seemingly unrelated substances, but, the list of common allergens is curiously consistent. The pollen of ragweed is one of the first known allergens, while the connection between intestinal distress and one food, milk, was recognised more than 2 centuries ago. Most drugs are too small (mol. wt less than 1,000), to be able to stimulate an allergic reaction, but they can act as incomplete antigens or 'haptens' which become complete antigens in combination with a body protein. The penicillins and the sulphonamides are two classes of drugs which frequently cause an allergic reaction. Cross allergy within a chemical group is usual, while allergy between two chemicals of similar structures such as penicilins and cephalosporins is also usual.