Total epidermal necrosis and subepidermal macules are one of the symptoms of toxic necrotizing epidermolysis bullosa drug rash. Most drugs have the potential to cause drug rash, including herbal medicines, but those with stronger antigenicity cause the most. Most of them are sulfonamides, salicylates, antipyretic and analgesic drugs such as pautazone and aminopyrine, phenolphthalein, penicillin, tetracycline, barbiturate, phenytoin sodium, etc. In addition, there is a greater risk of drug rash in patients with congenital allergic diseases of the organism and in patients with diseases of vital organs. Drug rash is a medical disease, therefore, the prevention of drug rash must be noted: 1, before using drugs should ask the patient what kind of allergy history, avoid the use of drugs known allergies or similar structure. 2, the use of drugs should be targeted, try to use less allergenic drugs. The early symptoms of drug rash should be noted during treatment, such as the sudden appearance of itching, erythema, fever and other reactions, the suspected drug should be immediately stopped, closely observed and strive to identify the allergenic drugs. 3, the application of penicillin, serum, procaine and other drugs should be made in accordance with the prescribed method of skin testing, positive can not be treated with the drug. Before the skin test, emergency drugs should be available to meet the urgent needs. The current national concentration of skin test solution is penicillin 500u/ml, streptomycin 5mg/m1, procaine 0,25%, tetanus antitoxin 1:10, the dosage is 0,1m1. 4, has been diagnosed as drug rash, the allergenic drugs should be recorded in the medical record and asked the patient to remember, every time you visit the doctor should tell the doctor not to use the drug.