Reticular cyanosis is a skin spasmosis, a skin manifestation of certain diseases, and some normal people also develop reticular cyanosis in cold environments. Gangrene is a specific morphologic change of black and dark green color due to secondary infection by spoilage bacteria and other factors after tissue necrosis. Both are seen together in the skin lesions of polyarteritis nodosa. Polyarteritis nodosa, also known as periarteritis nodosa and necrotizing arteritis, polyarteritis, etc., is a fatal disease. The clinical course is rapid and extensive, usually involving the systemic arterial system, and the clinical manifestations are complex and variable, depending on the site or organ involved. The clinical manifestations are complex and vary according to the site or organ involved. Because polyarteritis nodosa can be caused by a variety of etiologies, preventive measures should be taken from all aspects of common allergy-inducing drugs such as penicillin, ampicillin, streptomycin, Pioneer V, salicylic acid preparations, low molecular dextran, etc. Preventive, dietary therapy. Diet should be nutritious, easy to digest food, avoid spicy, tobacco, alcohol, greasy, fried food, etc.. In addition should also do the following. 1, avoid the abuse of drugs. Any drugs (including Chinese medicine, Western medicine) are used to treat diseases, have certain side effects, so we should oppose the indiscriminate use of drugs, even if there is a disease, we should strive to use less drugs, or through the strengthening of physical fitness, increase the resistance to disease, so that the disease will be cured. For example, if the elderly have a cold, if there are no serious symptoms, you can pay attention to keep warm and drink more water to promote the elimination of viruses. 2.Prevent drug allergy. Common drugs that can cause allergies are penicillin, ampicillin, streptomycin, Pioneer V, salicylic acid preparations, low molecular dextrose, etc. 3.Prevent infection. The elderly body resistance is poor, easy to infect bacteria or viruses and cause disease, common infections are: upper respiratory tract infection, urinary tract infection, biliary tract infection, etc., if the infection should take antibacterial drugs or Chinese medicine in a timely manner. 4, active treatment of hepatitis B. Some of the nodular polyarteritis is caused by hepatitis B, so active treatment of hepatitis B has some significance. You can take antiviral drugs such as Banlangen flush. 5, diet therapy. Diet should be nutritious, easy to digest food, avoid spicy, tobacco, alcohol, greasy, fried food.