Cefodizime sodium skin test preparation was diluted a total of three times, dissolving the drug every 0.5 g to dissolve 2 ml, the second dilution of the remaining 0.2 ml, and the third time then diluted to 1 ml. 1. Take a 0.5g/vial of cefodizime sodium, and dissolve it to 2 ml by drawing 250mg/ml sodium chloride injection with a syringe. 2. For the first dilution, draw 0.1 ml of 250 mg/ml solution and add saline to 1 ml to make a 25 mg/ml solution. 3. For the second dilution, 0.1 ml of 25 mg/ml solution was withdrawn and added to saline to 1 ml to prepare a 2.5 mg/ml solution. 4. For the third dilution, 0.2 ml of 2.5 mg/ml solution was extracted and added to saline to 1 ml to formulate a 0.5 mg/ml solution. The concentration of cefodizime sodium skin test solution prepared after the above steps is 500 micrograms per milliliter, and 0.1 milliliter should be taken when doing skin test, and the patient should be asked about the history of penicillin allergy during the skin test.