Skin tests cannot always be done with one needle and most needles, except indwelling needles, are not reusable. Skin test is a common clinical specificity test, mainly to determine whether certain drugs in the clinical use of the process of allergic reactions. When doing skin tests, generally use disposable syringes and needles, can not be reused to avoid cross-infection. And in the clinic, most of the medical needles are disposable and cannot be used repeatedly. Only the indwelling needle is to leave the catheter in the blood vessel, which can be used repeatedly. And the needle is only suitable for intermittent, continuous or daily need for intravenous infusion of patients, and only for short-term or single-dose administration, mainly to reduce the patient’s fear of injections. Therefore, patients usually need to choose regular medical institutions for infusion or skin test, etc., to avoid infection caused by repeated use of needles. Whether in the skin test or infusion, the vast majority of the need to use disposable, to avoid serious consequences.