Skin test is short for skin (or intradermal) sensitivity test, which is the most commonly used clinical specificity test. The most commonly used in the clinic is intradermal test, taking penicillin as an example, usually 0.1 ml of skin test solution is used, and a skin mound with a diameter of 0.3-0.5 cm is injected into the inner forearm. A normal skin mound is white or close to the color of the skin, with no redness, swelling or itching, which is the normal color of the skin test. Observe the skin test for about 20 minutes after injection, mainly to observe whether the dermatome has increased in size, redness and swelling. If the dermatome reaches 1 cm or localized redness, itching and other symptoms, are positive, suggesting that the use of such drugs is not suitable. Therefore, clinically, some drugs in the intravenous infusion need to do skin test, to avoid the infusion of drugs after the human body allergic reactions, severe allergic reactions and even life-threatening, injection of such drugs before the need to inject skin test.