More than 50 million people have allergies in the United States. Allergy Testing is imperative to finding the cause behind persistent allergic symptoms.
Allergy testing can be done at any age and may involve either skin or blood testing (Allergy RAST Testing). 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 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. If there is redness, swelling or 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.
A second set of testing, intradermal testing is performed if the scratch testing is negative. Intradermal testing consists of the allergens being injected under the skin. This method may pick up reactions the scratch testing may have missed. These results are also read within 20 minutes after applying.
Skin testing may cause itching or redness associated with positive skin test reactions. These usually subside in a few 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. Allergy skin tests may in rare occasion cause generalized allergic reactions such as rashes, shortness of breath, or anaphylaxis.
Allergy blood tests, also called RAST testing can be an alternative to allergy skin testing. Allergy blood tests may be recommended for young children, patients with chronic skin conditions and those who may be on a necessary medication that would interfere with skin testing.
The tests alone do not diagnose allergies. They must be interpreted in conjunction with the patient’s history and symptoms. A complete allergy evaluation would be the best approach to diagnosing and treating one’s allergies.