A lot of black spots on the arm are commonly seen in pigmented nevus, coffee spots, flat warts, seborrheic keratosis and other diseases, which need to be clearly diagnosed and then treated with medication, physical therapy, surgery and so on. 1. Pigmented nevus:For smaller pigmented nevus, laser treatment can be used to remove the pigmented nevus. For larger pigmented nevus or those with the possibility of cancer, timely surgical excision is necessary. 2. Coffee spots:After the diagnosis of this disease, Q-switched laser, intense pulsed light and other physical treatments can be taken to break down the melanin vesicles, and then with the body’s metabolism out of the body, so as to remove the coffee spots. 3. flat warts: for mild to moderate flat warts, through the carbon dioxide laser, high-frequency electric knife and other photoelectric treatment; can also use recombinant human interferon α-2b gel, vinblastine class of drugs; for a larger number or long time flat warts, you can use the immunomodulator treatment, such as cimetidine, levamisole, etc.; the number of small, take physical therapy. 4. Seborrheic Keratosis Pilaris: After the diagnosis of this disease, physical therapy can be taken, such as freezing, intense pulsed light, carbon dioxide laser, etc.; but also through surgical treatment, such as scraping, chipping, etc., to remove the warts. It is recommended that patients go to a regular hospital, after a clear diagnosis, follow the specialist doctor’s instructions reasonable treatment, the use of drugs need to be used under the guidance of the doctor, not blindly self-medication.