Penicillin skin test is still required after one month of four penicillin injections. According to the Pharmacopoeia of the People’s Republic of China Instructions for Clinical Use of Drugs, “patients are required to do penicillin skin test before using penicillin antibiotics”. Whether it is adults or children, oral, intravenous or intramuscular route of administration, the application of penicillins should be skin test before the application of penicillins, change the batch number needs to be re-skin test, stopping the drug for more than 72 hours, should be re-skin test. Because the body’s immune system is constantly changing with the body’s response, even if the same drug, before not allergic, after the allergy may also appear, as long as it is not continuous medication, more than 72 hours are required to carry out a skin test. Therefore, although the patient has received four injections of penicillin, a penicillin skin test is still required after one month. Therefore, before applying penicillin treatment, it is recommended to strictly follow the doctor’s instructions for skin test to prevent allergic reactions.