Allergy and Inflammation Conditions, Diagnosis and Testing
Conditions
The Division of Allergy and Inflammation cares for patients with a range of allergic conditions, including but not limited to:
Diagnosis and Testing
Allergies can be diagnosed by your doctor through a physical exam, family and symptom history, and/or allergy tests. Allergy tests can be done to help identify if you are allergic and what you are allergic to. Once allergies are identified, specific avoidance and treatment measures can be recommended.
What types of allergy testing can be done?
Scratch Skin TestingA reliable test for allergies is the scratch skin test. A small amount of each thing you may be allergic to (allergen) is placed on the skin—often the forearms. The skin is then pricked. If you are allergic to an allergen, you will get a bump and redness where the skin is pricked. After a short time, each skin test reaction is measured for swelling and redness. If there is a large enough skin reaction, it means that you may be allergic to the allergen placed at that site. The information from your prick skin test results and your history of symptoms will help your doctor to determine if you have an allergy.
Intradermal Skin TestingAnother form of skin testing for allergy is by intradermal skin testing. This method is not as reliable as prick skin testing. It is most often used when prick skin testing is negative and there is a strong suspicion of allergy from the history. A small amount of each thing you may be allergic to (allergen) is placed under the skin with a needle, usually on the arm. If you are allergic to an allergen, you will get a bump and redness where the needle has gone under the skin. After a short time, each skin test reaction is measured for swelling and redness. If there is a large enough skin reaction, it means that you may be allergic to the allergen placed at that site. The information from these test results and your history of symptoms will help your doctor to determine if you have an allergy.
Antihistamines and other medicines can also affect these skin test results. Ask your healthcare provider what medicines to avoid before your skin tests are done.See our Skin Test Information Pamphlet »
Blood TestingA blood test is another kind of test that can be done to help find out if you have allergies. There is some evidence that blood tests are not as sensitive as prick skin tests in determining allergies. However, 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. The most common one is called RAST testing.
Positive skin or RAST tests help narrow the list of suspected allergens, but don't often point directly to the cause of symptoms. The patient's history is vital in determining which of the positive skin test or RAST results really contribute to allergy symptoms. A challenge test may also be needed. If the patient's allergic reactions haven't been severe, the physician might deliberately expose the patient to one or more substances that produced a positive skin or RAST test. This is particularly true with food allergies.
Patch Skin TestingPatch skin testing may be used to find out if a rash is from direct contact with an allergen. Patch tests are not the same as skin prick tests, which are used to diagnose hay fever allergy (house dust mite, grass pollens and cat dander). Skin prick tests have very limited value for patients with skin rashes.
A range of substances can be used for patch testing. Each substance has been tested to find the best concentration to demonstrate an allergic reaction without causing irritation to those who are not allergic to the material. Patch tests do not always explain the cause of a dermatitis.
Several appointments are necessary for the application, removal, and interpretation of the patch test.
