Allergy can be defined as the overreaction of your body when exposed to things that don’t cause problems for most people. The overreaction can be inflammation of your skin or it can be in the form of coughing, vomiting, scratching, hay fever, etc. The substances that cause you such things are called allergens.

An allergy skin test is performed to know exactly what is causing allergy to a person. Small amounts of different known allergens are put onto your skin to see which ones you react to. Once it is confirmed which allergens you are allergic to, you know what is causing you allergy. Besides skin test, blood tests such as the ELISA test or radioallergosorbent test (known as RAST) are also performed in order to know the cause of allergy.

Another way of understanding what causes allergy is presented in the following.

Basics: An educational error of the bodies’ immune system is the reason allergy happens. Normally, the immune system is used by the body to defend itself against foreign invaders such as viruses and bacteria through experience i.e. encouraging, battling, and then remembering one enemy after another. Invaders that the immune system has seen before are better tackled by it than those the system first encounters. Using unique protein molecules known as antibodies and special memory white blood cells this process is accomplished.

Continuing the above we can know what causes allergy. When the immune system misidentifies harmless foreign substances and reacts to them as if they were as harmful, allergic reactions occur.