Intradermal (ID) testing is not commonly used but can be helpful in diagnosing suspected drug, venom, or vaccine allergies. Unlike skin prick testing, which is more commonly performed, ID testing involves injecting very small amounts (0.02 ml or 1/1500 of an ounce) of the potential allergen into the surface layer of the skin using an extremely tiny needle, similar to the process used for tuberculosis screening. The injection site is then monitored for 20 minutes to observe for any local reactions, which may indicate an allergic response.

Notably, ID testing is approximately 1000 times stronger than skin prick testing. However, it is not generally used for suspected food or environmental allergies.