immune disorders
Overview of Allergic Reactions
Introduction
Allergic reactions (hypersensitivity reactions) are inappropriate responses of the immune system to a normally harmless substance. Usually, allergies cause sneezing, watery and itchy eyes, a runny nose, itchy skin, and rash. Some allergic reactions, called Anaphylactic Reactions , are life threatening. Symptoms suggest the diagnosis, and skin testing can help identify the substance that triggers the allergy but does not predict the severity of a future reaction. Avoiding the trigger is best, but if it is impossible, allergy shots, when given long before the exposure occurs, can sometimes desensitize the person. People who have had or are at risk of having severe allergic reactions should always carry a self-injecting syringe ofepinephrineand antihistamine pills. Severe reactions require emergency treatment in an emergency care facility. Normally, the Overview of the Immune System —which includes antibodies, white blood cells, mast cells, complement proteins, and other substances—defends the body against foreign substances (called Allergens may cause an allergic reaction when they land on the skin or in the eye or are inhaled, eaten, or injected. An allergic reaction can occur in several ways: Triggered by substances present only during certain seasons, such as tree, grass, or ragweed pollens ( Seasonal Allergies , including hay fever) Triggered by taking a drug ( Allergies to Drugs ) Triggered by eating certain foods ( Food Allergy ) Triggered by breathing in dust, animal dander, or molds ( Year-Round Allergies ) Triggered by touching certain substances (such as latex) Triggered by insect bites or stings (as occurs in Anaphylactic Reactions and In many allergic reactions, the Overview of the Immune System , when first exposed to an allergen, produces a type of Some people have an inherited tendency to produce a lot of IgE (a condition called atopy) and may overreact to some antigens that cause hay fever, asthma, skin problems, or a food allergy. 