Red, itchy arms first need to clarify the cause of the disease, such as urticaria, contact dermatitis, eczema, etc., need to use the general treatment of the cause, medication to improve. 1. Urticaria: refers to a variety of internal and external factors caused by a perverse reaction, the formation of limited elevated in the skin, mucous membrane surface edema mass, may be conscious of itching. First of all, attention should be paid to remove the cause of the disease, if the patient is suspected of drug-induced urticaria, such as angiotensin-converting enzyme or non-steroidal anti-inflammatory drugs, need to stop the drug or replace it with other drugs; if you suspect that the food-induced urticaria, you need to look for possible foods and avoid them in a timely manner. Oral antihistamines such as loratadine should be taken according to the treatment program. 2. Contact dermatitis: inflammatory skin disease caused by skin contact with external irritant, allergic substances, need to avoid contact with irritants and sensitizing substances, serious cases need to be applied under the guidance of the doctor glucocorticosteroids such as mometasone furoate cream to reduce the symptoms, but also the application of antihistamines such as ibrastine to relieve itching. 3. Eczema: a chronic inflammatory itchy skin disease, multiple ring-shaped rash, symmetrical distribution. It requires long-term treatment. You can apply local glycerine lotion, glucocorticoid cream such as halometasone to reduce the skin lesions, if necessary, oral antihistamine drugs. It is recommended that the arm redness, itchy timely consultation, identify the cause, under the guidance of the doctor standardized treatment, do not self-medication.