Allergies occur when your body mistakes a normally harmless substance (called an allergen) as a threat and attacks it. Your body will release a specific antibody called Immunoglobulin E (IgE) which causes the release of inflammatory chemicals such as histamine. Histamine cause the symptoms commonly associated with an allergic reaction, such as sneezing, runny nose, hives and watery eyes.
In order to treat your allergy symptoms, your doctor will first need to figure out what you are allergic to. This is usually done through a skin test, or a blood test.
A skin allergy test involves placing a small amount of what you may be allergic to (called an allergen extract) on or below the skin. There are two main types of skin tests: a skin prick test, and an intradermal test.
A skin prick allergy test requires a drop of the allergen extract to be placed on the skin, and a needle is used to either scratch or prick the skin through the drop. This allows the extract to enter the skin. After 15 minutes, the red, raised and itchy areas that have developed are measured. This is usually an indication that you are allergic to the allergen.
An intradermal test is more sensitive. The allergen extract is injected into the skin. After 15 minutes any red, raised and itchy areas are measured. It also serves as a basis for starting immunotherapy (allergy shots).
A blood test is used to measure the amount of allergy specific IgE antibodies in your blood. This test is used when the individual’s skin is too sensitive for a skin test, if they cannot stop taking medications that will affect the results of a skin test or they are too allergic and a skin test could result in a life-threatening reaction.