Allergies Skin Testing for Allergies Print By Daniel More, MD | Medically reviewed by a board-certified physician Updated February 28, 2018 More in Allergies Nose & Eye Allergies Drug & Latex Allergies Contact Dermatitis Food Allergies Skin Allergies Animal & Insect Allergies Urticaria & Angioedema Common Treatments Skin testing for allergies is a time-tested and easy procedure. Follow along on this pictorial to see the process unfold on a young patient. 1 Preparing the Skin for Testing Daniel More, MD The skin is prepped for testing by allergy testing with rubbing alcohol, typically on the back or arm. 2 Skin Testing Devices Daniel More, MD There are many skin testing devices for allergy testing. Many perform multiple skin tests on a single device. This is a multi-headed skin test device that allows five skin tests to be placed at once. The device has a small metal point that is dipped into allergen extracts, then pushed into the skin. 3 Marking the Skin Daniel More, MD The skin is marked with a surgical marker in order to keep track of which skin test site represents which allergen. 4 Ready for Skin Testing Daniel More, MD The skin is now ready for allergy tests to be placed. 5 Skin Testing Procedure Daniel More, MD The skin test procedure involves gently pressing the skin test device into the skin, with metal or plastic tips puncturing just the top layer of the skin. This causes the allergen extracts to enter the top layer. This form of skin testing is termed "puncture," which is a variation of the scratch or prick test. Skin testing is not painful. 6 Completing the Skin Test Daniel More, MD A number of skin tests are placed, depending on the symptoms of the patient and what the allergist to trying to determine are the possible causes of the person's allergy symptoms. Depending on the age of the person and the reason for testing, this may range from 10 to 70 or more skin tests. 7 Blotting the Skin Daniel More, MD Excess allergen extract is removed from the skin by blotting with paper towels. This is so that the liquid will not run into adjacent skin testing sites, causing false reactions. 8 Waiting 15 Minutes Daniel More, MD A timer is set for 15 to 20 minutes, allowing time for the skin tests to react prior to reading the results. They may not take that long to react. 9 Reading the Results Daniel More, MD The skin test results are read at 15 minutes. A positive test shows a wheal (bump) and flare (redness) reaction. These are measured and compared to the positive and negative controls. The size of the reaction determines whether the test is positive or negative. 10 Close-up of Results Daniel More, MD A close-up of the results shows a significant positive reaction to an allergen as a result of skin testing. The site may be very itchy, but the rash and itching will go away without treatment within an hour or so. The wheal and flare reaction may be of unusual shapes, indicating a strong reaction. 11 Skin Testing Complete Daniel More, MD The skin test is now complete and the results can be interpreted by the allergist. Some allergists recommend that the patient remains in the clinic for up to 30 minutes to ensure that unexpected side effects do not occur. Side effects from skin testing are extremely rare. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Email Address Sign Up There was an error. Please try again. Thank you, , for signing up. What are your concerns? Other Inaccurate Hard to Understand Submit Continue Reading