The inflammatory reaction of the skin and mucous membranes caused by the entry of drugs into the body is called drug rash. Drug rash is the most common type of drug reaction. The causes of drug rash are complex and closely related to the pharmacological effects of the drug, toxic effects, allergic reactions, and the specific constitution of the person. Patients should generally have a history of drug use and the rash subsides after stopping the drug. The rash usually starts suddenly, with red, itchy and symmetrical distribution, starting from the face and neck, then spreading to the upper limbs, trunk and lower limbs, or accompanied by chills, fever and general malaise. In mild cases, the rash gradually subsides after stopping the medication, but in severe cases, it can be life-threatening. There are various types of drug rashes, often resembling the rash of an infectious or skin disease, so the name of the disease can be used, such as urticaria, papules, erythema, scarlet fever-like rash, angioneurotic edema, blisters, purpura, eczema, exfoliative dermatitis-type drug rash, etc. Clinically, drugs that can cause drug rash include: a. Sulfonamides, sodium phenytoin, phenobarbital, sodium p-aminosalicylate, and pterostilbene, which can cause exfoliative dermatitis-type drug rash. This kind of drug rash can occur after 20 days of medication, initially as a measles-like, scarlet fever-like, accompanied by chills, fever, followed by general flushing, swelling, to the hands, feet, face as heavy. Afterwards, the skin of the whole body flakes off, the hands and feet peel off in a large area in the form of gloves or socks, some finger (toe) nails and hair fall off, the mouth and lips are red and swollen, and the conjunctiva of the eyes is congested. Severe with kidney, liver damage, and accompanied by high fever, coma, and even death. Second, penicillin, dysentery, sodium salicylate and serum products (such as tetanus antitoxin) are likely to cause urticaria-type drug rash. After the use of drugs, the onset of the disease is urgent, the skin suddenly itchy and quickly appeared in varying sizes of bright red, round, oval or irregular-shaped, scattered on the head and face and limbs and trunk, and the phenomenon of rising and falling. In more severe cases, vomiting, fever and arthralgia may occur. Third, antipyretic and analgesic drugs, hypnotics, sedative drugs, sulfonamides, penicillin and streptomycin are prone to cause fixed drug rash and measles-like or scarlet fever-like drug rash. The rash is one or several round edematous erythematous spots of varying sizes, with large blisters on the erythematous spots, with itching and burning pain, which will subside if the drug is discontinued, and the same drug rash can appear at the original site if the same drug is taken again, so it is called fixed drug rash. Measles-like or scarlet fever-like drug rash has a rapid onset and is accompanied by chills, fever and other systemic symptoms. The rash of measles-like drug rash is a scattered or dense, pinpoint or rice-sized red rash or maculopapular rash that is symmetrically distributed, with the trunk being the most common. Scarlet fever-like drug rash is a small erythematous rash that progresses from the face, neck, upper extremities, and trunk downward. Fourth, mercury agents, quinine and sulfonamides can cause eczema-type drug rash. It is polymorphic and can have changes such as erythema, blisters, papules, pustules, vesicles and oozing. Often due to the topical use of sulfonamide or antibiotic ointment, the skin sensitivity first increased, and later take the same kind of drugs, can cause drug rash. It improves when the drug is discontinued. Avoid drug rash to pay attention to the following points: 1. Do not use drugs at will. The person inevitably gets sick, but not all diseases need to be medicated, some diseases can be self-healing without medication, such as the flu. Some diseases that can be treated through physical exercise, physical therapy, etc., should also try not to use drugs. Frequent use of drugs will seriously damage the body’s anti-illness self-healing power, so that people’s physique decline and often get sick, then use drugs is not so spiritual. 2, do not take drugs according to the advertising. Some drug advertisements highlight the efficacy of propaganda and have no time to take into account or intentionally avoid adverse reactions. Some new drugs with the increase in clinical application, its adverse reactions also gradually increased. Look at the ads to take drugs is difficult to do the right medicine, and even serious adverse reactions or pharmacogenic diseases. 3, careful use of expensive drugs, new drugs. The effectiveness of drugs can not be measured by the price, the key is whether the symptom, the efficacy and the number of adverse reactions. There is no direct relationship between the price and efficacy of drugs. Drug prices are determined by pharmaceutical costs, production processes and advertising and other factors. Therefore, the high price of the drug is not necessarily a good drug. 4, do not mix drugs. Some patients often put a variety of drugs together to take. They believe that the mix of drugs, can increase the efficacy. This view has a one-sided. Because some drugs together will make the drug effect will be weakened or offset, toxic side effects enhanced.