Vitamin C plus calcium for desensitization is commonly used in emergency departments and the number of days needed depends on the condition. In case of transient food allergy, which does not cause obvious other organ diseases, it is only necessary to hang for 1-3 days. Use 5% glucose injection 250ml, add vitamin C.5.0g for injection and 10mg of calcium gluconate. In case of severe allergy, with the appearance of skin rashes and papules, fusion into a windy rash, fusion into patches, and even the presence of vesicles and oozing, it is necessary to apply desensitizing drugs for at least 3-5 days. If the patient’s condition is more serious, with severe clinical symptoms such as anaphylaxis or the presence of allergic combined cardiovascular and cerebrovascular diseases, it is necessary to order vitamin C plus calcium treatment for at least about 10-14 days.