Intradermal skin testing is used in some cases to help further evaluate environmental allergy when the skin prick test does not show any allergies, yet there is still suspicion that the patient is allergic. It is also used for drug and venom allergy evaluations. It is never used to diagnose food allergy. This procedure usually follows negative skin prick testing in select patients. A small needle is inserted into the top of the skin and a small amount of allergen is injected, creating a small bubble. The test is then read 15-20 minutes later. Multiple intradermal tests can be placed during a visit to assess allergy to multiple items in question. If you believe you will be undergoing intradermal testing for allergies, please remain off medications such as antihistamines for at least 5-7 days prior to testing.