Pharmacologic dermatitis and contact dermatitis are two different skin diseases with different causes, symptoms and treatment principles. 1. Different causes: the cause of drug dermatitis is clearly related to the drug factor, which means that the drug enters the body through oral, topical or injection, and then produces an adverse allergic reaction, bringing serious harm to the skin’s health. The cause of contact dermatitis is related to contact with irritating substances, leading to skin allergic reactions and skin damage. 2. Symptoms are different: drug dermatitis lesions can be manifested in a variety of skin manifestations all over the body, manifested in localized dark purple rash, urticaria-like rash, scarlet fever-like rash, purpura-like rash, polymorphic erythema-like rash and so on. Contact dermatitis lesions are often limited to the contact area. 3. treatment principle is different: drug dermatitis treatment principle is the need to stop using drugs, as soon as possible to eliminate drug reactions, prevent and timely treatment of complications. Contact dermatitis treatment principle is to find the cause of the disease, rapid detachment from the contact material and active symptomatic treatment. After the cure should try to avoid re-exposure to allergens to avoid recurrence. Visible drug dermatitis and contact dermatitis have a lot of difference, if there are suffering from these two diseases, it is recommended to go to the dermatology department in time for examination, under the guidance of the doctor for targeted treatment.