Itchy arm skin may be related to physiological factors such as poor hygiene habits, or it may be caused by diseases such as insect bite reactions, eczema and ringworm. 1. Physiological factors: itchy arm skin may be related to poor hygiene habits, if the daily skin cleaning less often, it may trigger local dirt, thus triggering itching. 2. Insect bite reaction: the cause of its more and more insect bites the body secretion, patients will appear erythema, blisters and other symptoms, more conscious of itching, common in the waist, buttocks and limbs and other places. 3. eczema: eczema is usually manifested as erythema, edema, itching and blisters and other symptoms, commonly found on the head and face, hands and feet and limbs and other places. 4. Tinea corporis: clinical manifestations of papules, blisters and erythema, often occurring in the trunk, arms and other exposed areas, accompanied by varying degrees of itching. The cause of its formation may be red trichophyton, canine microsporidium and other dermatophyte infection. There are more reasons for itchy arm skin, and after excluding physiological factors, patients are advised to seek medical examination to clarify the cause.