Allergy: Diagnosis

Allergy Tests

Allergy tests can be done to help identify if you are allergic and what you are allergic to.

• Prick Skin Testing: With prick skin testing, a small amount of each thing you may be allergic to (allergen) is placed on the skin - often the back. The skin is then pricked. If you are allergic to an allergen, you will get a bump and redness where the skin is pricked.

• Intradermal Skin Testing: Intradermal skin testing is most often used when prick skin testing is negative and there is a strong suspicion of allergy from the history.

• Blood/RAST Testing: A blood test may be done if you have skin problems or if there is concern that someone will have a severe reaction to a skin test (this is very rare). There are many types of blood tests that can be used to detect allergies, but the most common one is called RAST.

• Patch Skin Testing: Patch skin testing may be used to find out if a rash is from direct contact with an allergen. Small amounts of allergens are placed on the skin, often the back. The skin is covered with a watertight bandage for several days. After several days the patch is removed and the skin reactions are measured to find out if you may have a contact allergy.

• Food Challenge: If you have a positive skin test to foods, your doctor may consider a food challenge. In some cases, this test is the only way to make a diagnosis of food allergy. Increasing doses of the suspected food are given and you are checked for symptoms.

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