The causes of a ring of flesh on the small of the arm can include skin scratches disorder, scarring, and ringworm. 1. Skin scoring disorder: Skin scoring disorder is a common type of induced urticaria, also known as artificial urticaria. Mechanical stimulation (scratching, scratching, scratching, etc.) on the patient’s skin produces an increased physiologic response, resulting in the production of striae on the skin within a few minutes. 2. Scarring: seen after the healing of wounds deep into the dermis caused by trauma, ulcers and local inflammatory lesions. Clinical manifestations of localized elevated pink or purple-red lumps, the surface is congested, hard, the edge does not protrude into the normal skin, accompanied by itching and pain. Striated scarring can be manifested as skin with striated flesh ring. 3. Tinea corporis: Tinea corporis lesions are initially red papules, papules or small blisters, followed by the formation of scaly red patches with clear borders, the edges are constantly expanding outward, and the center tends to subside, forming a clear border ring or multiple rings. It may appear as a ring of flesh on the skin. There are other reasons for the phenomenon of a ring of flesh on the arm, please go to the hospital in time to check, follow the doctor’s advice and reasonable treatment.