Allergy Skin Test

Description of the test

An allergy skin test identifies which substance triggers an allergic reaction. A small amount of the substance, or allergen, is introduced to the body through the skin. If the skin reddens or swells then the test is read as positive and the person is probably allergic to that substance. The reaction is due to the release of histamine, a chemical naturally found in the body, which causes swelling, redness, and itching (also known as a wheal). This test is performed by an allergist.

How often should this test be performed?

Your doctor will decide when and how frequently this test is required.

Why is this test performed?

Allergy skin tests are performed to identify what allergen is causing allergy symptoms (such as sneezing, nasal congestion, itchy eyes, wheezing, skin rash, and swelling) so that people can avoid the trigger if necessary. There are many allergens - including foods, medications, and environmental substances (such as ragweed and fungus), as well as contact allergens which irritate the skin.

Allergy skin tests take place when allergy shots are being considered. Testing may also be necessary for people with serious allergic rhinitis or asthma.

Are there any risks and precautions I should I know about?

Some people have extremely serious allergic reactions, called anaphylactic reactions. If a person has had an anaphylactic reaction to an allergen in the past, they may not have an allergy skin test for this substance as the test might provoke a dangerous reaction.

The most serious risk of having a skin prick test is anaphylactic reaction. This reaction is a medical emergency, causing difficulty breathing and a dangerously low blood pressure. However, anaphylactic reactions with skin prick tests are rare and the allergist will be monitoring you closely.

Skin testing may not be performed if you have certain skin conditions, such as severe eczema or atopic dermatitis.