Allergic reactions are caused by the body’s immune system overreacting to a substance that is not harmful. Common causes of allergic reactions are certain types of food (e.g., peanuts, soy, dairy, wheat, eggs, and shellfish), seasonal or environmental substances (e.g., dust, mold, pollen, and ragweed), animals (e.g., cat hair, dog dander, insect bites, and cockroaches), and medications (e.g., penicillin, ibuprofen). The substances that cause allergic reactions are called allergens.
An allergic reaction begins when the person with the allergy is exposed to an allergen, usually by swallowing it, inhaling it, or touching it. The person’s immune system reacts by creating a type of antibody, called immunoglobulin E (IgE). Antibodies are the weapons the body’s defense (immune) system uses to attack substances that may cause harm, such as bacteria and viruses. In the case of an allergy, the IgE attaches to mast cells, which are a type of blood cell that can usually be found in the airways and...
- The Food Allergy & Anaphylaxis Network: http://www.foodallergy.org/. Accessed June 16, 2011.
- Mayo Foundation for Medical Education and Research: http://www.mayoclinic.com/health/allergies/DS01118. Accessed June 16, 2011.
- National Institute of Allergy and Infectious Diseases: http://www.niaid.nih.gov. Accessed June 16, 2011.
- WebMD Allergies Health Center: http://www.webmd.com/allergies/. Accessed June 16, 2011.