Hello, It is an adverse reaction of the body either to food or substances in the environment. Any substance, which triggers an allergic reaction, is called an allergen. It may be pollen, house dust mites, mold, pets, nuts, fruit and latex. When there is release of chemicals which leads to allergic reaction, whenever the body comes in contact with the above substances is a result in allergic reaction with symptoms such as rash, sneezing, flushing of the face, itching and in severe forms leading to anaphylaxis. Allergic are very common where the individual experiences one way or the other. Whenever a person s immune system reacts to an allergen, it produces an antibody called as IgE to fight. When you develop any of the allergic symptoms, it is better to contact your doctor who can go through your history in detail and arrange for a skin prick test, blood test and a patch test (in case of contact dermatitis). Regarding the treatment, it is best to avoid contact, antihistamines, decongestants, Leukotrine receptor antagonists, steroid spray, hyposensitisation (Immunotherapy), if there is any anaphylactic reaction, it should be treated immediately. You can also use tablet cetirizine at bedtime for 3 day to reduce the itching. It looks like you have a food allergy which depends on what you ate and your body s immune response you it. I would suggest you to consult your physician for the further management. Thank you.