A lot of dark brown spots on the arm, consider and seborrheic keratosis, florid chaff rash, post-inflammatory hyperpigmentation spots and other factors related to the daily protection, topical medication, physical methods of treatment. 1. Seborrheic keratosis: Seborrheic keratosis is mainly caused by skin aging, hereditary factors, gene mutation, etc. This disease is common in the elderly over 50 years old, and can be induced by ultraviolet radiation, viral infection, and drugs. Can follow the doctor’s instructions for external use of Vitamin A suab medicine, pay attention to the affected area hygiene, avoid scratching, usually when you go out, you can wear long-sleeved or carry umbrellas. 2. florid chaff rash: arms appear a lot of dark brown spots, may also be due to malassezia invasion of the skin stratum corneum caused. Patients can follow the doctor’s instructions to apply topical terbinafine hydrochloride cream, miconazole cream and other drugs to inhibit fungal treatment. 3. Post-inflammatory hyperpigmentation: after arm trauma, local scratching stimulation and other factors lead to skin damage, the local pigmentation spots can be left behind, the patient can go to the regular hospital for treatment, topical drugs, including hydroquinone cream, etc., but also can be treated with laser, which can promote the decomposition of the local pigment cells, thereby alleviating the condition. During the treatment period, it is necessary to maintain sufficient sleep and avoid excessive stress.