Brian S. Lipson, M.D. – Allergy Testing
More than 50 million people have allergies in the United States. When people with allergies have persistent symptoms, it becomes imperative to find out what their allergies are to better treat their symptoms. It is the first step to an effective treatment for their allergies.
Once a thorough medical history and physical exam are conducted, it is imperative to proceed with allergy testing to identify the allergens triggering the patient’s symptoms.
Allergy testing can be done at any age and involve skin testing or blood testing (Allergy RAST Testing). Allergy testing should always be conducted under the supervision of a board certified allergist/immunologist to effectively interpret the results.
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Allergy tests can detect allergies to pollen, mold, dust mite, animal dander, insect stings, foods and some medicines.
Skin testing is done by scratching or pricking the skin with a plastic prong device containing the suspected allergen. The tests can be performed on the back or forearm. Multiple allergens can be tested at the same time. The site is observed for 20 minutes and then red. If there is redness, swelling and itching, it means the patient is allergic to that particular allergen. The size of the reaction will determine how sensitive the patient is to the allergen tested.
Sometimes, a second set of testing called intradermal allergy testing is performed if the first testing is negative. This is done just under the skin and picks up reactions missed by the first set of testing. These results are also read within 20 minutes after applying.
Skin testing causes little or no pain except for the itching and redness associated with positive skin test reactions. These usually go down in a couple of hours and can be treated with antihistamine medication if necessary. However it is crucial to stop all antihistamine medication 3-4 days before allergy skin testing.
Any medical test involves some risk. Allergy skin tests may in rare occasion cause generalized allergic reactions such as rashes, shortness of breath, or anaphylaxis. Fortunately these reactions are easily treated in the allergist office.
Allergy blood tests, also called RAST testing can be an alternative to allergy skin testing. It is most often used if the patient is taking a medicine that will interfere with the skin testing and cannot stop this medicine, has a chronic skin condition that would prevent allergy skin testing or babies and very young children where a blood draw would be better than multiple skin tests.
However allergy blood tests are more expensive than skin testing, take several weeks to get the results, rather than 20 minutes, and are less sensitive than the allergy skin testing. For every 10 positive allergy skin tests, the blood test will pick up approximately only 8 positive tests
Each testing method has its pluses and minuses. The tests alone do not diagnose allergies. They must be interpreted by the allergist in context with the patient’s history and symptoms. So a complete allergy evaluation by a board certified allergist would be the best approach to diagnosing and treating one’s allergies.
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