Allergies An allergy is a reaction by the immune system to something that does not bother most other people. People who have allergies often are sensitive to more than one thing. Substances that often cause reactions are
Normally, the immune system fights germs. It is the body’s defense system. In most allergic reactions, however, it is responding to a false alarm. Genes and the environment probably both play a role.
Allergies can cause a variety of symptoms such as a runny nose, sneezing, itching, rashes, swelling, or asthma. Allergies can range from minor to severe. Anaphylaxis is a severe reaction that can be life-threatening. Doctors use skin and blood tests to diagnose allergies. Treatments include medicines, allergy shots, and avoiding the substances that cause the reactions.