Introduction : In simple terms, an allergy is a hyperactive response of the immune system to certain substances which are "foreign" to our bodies. These substances are called "allergens", and they can range from food and pollen to dust and drugs.
Overview : Immune reactions are out of proportion to the damage caused by a pathogen, or the immune system produces a reaction to a harmless antigen, causing hypersensitivity reactions.
Immediate reaction The immediate reaction responsible for anaphylactic shock, angioedema, and hives is caused when IgE and antigens bind to basophils and mast cells, resulting in the release of chemical mediators such as histamine and platelet-activating factor.
Cont... These substances contract smooth muscle and cause an accumulation of extravascularfluid by increasing vascular permeability.
delayed-type hypersensitivity The delayed-type hypersensitivity reaction is mediated by a T-cell response rather than by antibodies and leads to granulomatous inflammation.Two examples of this reaction are inflammation resulting from a tuberculin test and contact allergy to a topical antigen.
Cont... The immune nature of an allergic reaction is well accepted, but the relationship of the immune response to other diseases remains controversial.
:Causes Allergic reactions are unique for each person. Reaction time to allergens can vary widely. Some people will have an allergic reaction immediately, for others it will take time to develop.
Cont... Certain foods such as peanuts, strawberries, shellfish, shrimp, dairy, and wheat. Vaccines and medications (antibiotics like penicillin, amoxicillin, aspirin, ibuprofen, iodine), general anesthesia and local anesthetics, latex rubber (such as in gloves), dust, pollen, mold, animal dander.