Allergy Skin Testing

Skin testing is one of the easiest and least expensive tests for detecting allergies. Skin testing is done by injecting an allergen (something that causes an allergic response) into the skin. The size of the wheal (tiny area of swelling) and flare (area of inflammation or redness) surrounding the area of the test, determine if it is positive. There are two methods of doing a skin test. One method is called the prick puncture test where the allergen is injected into the top layer of the skin (epidermis). Another method is injecting the allergen into the slightly deeper layer (dermis). More severe allergic reactions have been reported with this deeper injection. If skin testing has been performed and a questionable result is obtained, it can be confirmed by RAST. Two drawbacks to the RAST test are expense and the results are not being immediately available.


No preparation is necessary but the test should not be done if there have been severe allergic reactions such as anaphylaxis.


  • Less Than 3mm wheal diameter

  • Less Than 10 mm flare diameter

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.


Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.