The possible causes of arm redness and swelling include trauma, allergic diseases, infectious diseases and many other reasons. After clarifying the causes of the disease, general treatment, medication, surgery and other measures can be carried out according to the causes. 1. Trauma: external force causes local skin congestion and edema. In the early stage, the symptoms can be relieved by cold compresses, and usually no special treatment is needed. If the skin breaks down and becomes infected, drugs such as povidone-iodine can be used to sterilize the skin, and drugs such as mupirocin ointment can be used externally at the same time. 2. Allergic diseases: including contact dermatitis, insect bite dermatitis, urticaria and other diseases, is the allergen stimulation caused by local skin redness and swelling, may also be accompanied by itching and other discomforts, can be used externally dexamethasone cream and other antihistamines, and if necessary, can be taken orally cetirizine and so on. 3. Infectious diseases: due to local skin or soft tissue infection caused by redness and swelling, usually accompanied by fever, pain and other discomforts. Early local use of povidone-iodine, erythromycin ointment and other drugs, the emergence of systemic fever symptoms can use penicillin, cefuroxime and other drugs for anti-infection treatment. If the local pus cavity is formed, surgical incision and drainage is needed. It is recommended to go to the hospital in time when the above symptoms occur, and the drugs should be used under the guidance of the clinician.