An allergy skin test is the most reliable form of allergy testing and is still the mainstay of allergy testing. Skin prick testing has proven to be more accurate than blood testing in diagnosing allergies. These skin tests are easy and safe to do, give fast results, and are relatively inexpensive, which makes them the best way to start looking for specific allergy.
Many types of allergies can be confirmed with the use of skin testing, these include environmental allergens (pollen, molds, animals, dust mites), foods, stinging insects and medications.
What is Allergy Skin Test?
An allergy skin test is a method that allergists use to see whether a patient’s exposure to specific substances provokes an allergic response. This is typically done on the skin to check for an immediate allergic reaction. Testing is based upon each patient’s history of allergy symptoms including timing and severity. Most adults are tested on their forearms, but sometimes children are tested on their upper backs.
How is Skin-Testing for Allergies Done?
There are 3 common methods of allergy skin testing.
- Skin prick test. For this test, your skin is lightly scratched or pricked with a plastic device that contains a drop of extract with the possible allergen. Allergy is present if a small hive develops in the prick area within 15 minutes.
- Intradermal test. During this test, which is more sensitive than prick testing, a small amount of allergen solution is injected under your skin. Allergy is present if the area around the injection becomes red and itchy within 15 minutes.
- Patch test. A type of allergy skin test which does not involve lancets or needles. Patches containing allergy extract are placed on your skin for 48 hours. After removal, you will be checked the following day for local allergic reaction.
What Age is Appropriate For Allergy Skin Testing?
Per the American Academy of Pediatrics, age is not a barrier to skin testing. Even infants can benefit. As the child’s immune system develops, the child should be retested to identify changes in his/her immune response.
How to Prepare for the Tests?
Many medicines can affect the results of an allergy skin test. Examples include tricyclic antidepressants and antihistamines such as cetirizine (Zyrtec), fexofenadine (Allegra), and loratadine (Claritin).
Be sure to tell your allergist about all the medicines you take. You may need to stop taking medicines before you have an allergy skin test.
Is Skin-Testing Painful?
Patch skin-testing is relatively fast and painless. Also, prick skin-testing is not an uncomfortable procedure for most patients. Intradermal skin tests cause minimal discomfort as the allergen is injected. A positive result typically causes itching and local swelling which resolves in 1-2 hours.
What Do the Results Mean?
A negative test result means there were no skin changes in response to the allergen. This negative reaction most often means that you are not allergic to the substance. In rare cases, a person may have a negative allergy test and still be allergic to the substance.
A positive result means you reacted to a substance. Your provider will see a red, raised area called a wheal. Often, a positive result means the symptoms you’re having are due to exposure to that substance. A stronger response means you are likely more sensitive to the substance.
Your allergist will consider your symptoms and the results of your skin test to suggest lifestyle changes you can make to avoid substances that may be causing your symptoms.
Skin Tests Must Be Done by a Certified Allergist
An allergy skin test is an important diagnostic tool. All skin testing should be supervised by a board-certified allergist, who is trained to interpret testing in the context of history and physical exam findings. Additionally, there are rare events when testing can produce a severe and immediate reaction. A certified allergist is experienced to promptly and effectively treat a severe reaction with the proper medications and emergency equipment.