First of all, add 20ml of saline to a bottle of penicillin to dissolve it completely, take 0.1ml of liquid with a 1ml syringe, add 0.9ml of saline to configure it into 1ml of liquid, then take 0.1ml of skin test liquid again to add 0.9ml of saline, then take 0.1ml of skin test liquid again to add 0.9ml of saline, at this time the liquid of skin test is is successfully configured. If a skin test is needed, 0.1ml of the test solution should be injected into the inner skin of the patient’s forearm. After the injection, the patient should be observed to see if there is any reaction, usually to see if there is a faster heart rate, lower blood pressure, difficulty in breathing, etc. Generally, 15-20 minutes later to observe whether the skin test is positive or negative.