Arm long brown spots may be caused by hyperpigmentation, sun spots, seborrheic keratosis, etc. Patients should seek timely medical attention to clarify the cause of the disease and then carry out the corresponding treatment. 1. Hyperpigmentation: caused by cosmetics, pregnancy, hereditary factors such as epidermal or dermal pigmentation caused by the increase in the patient can be manifested as brown spots on the skin, such people should do a good job of sunscreen. 2. Sun spots: brown spots on the arm may also be sun spots, such patients in the spot before the emergence of a long time to receive strong ultraviolet radiation. 3. Seborrheic keratosis: the etiology of seborrheic keratosis is unknown, and it may be related to skin aging, sun exposure and other factors. It is characterized by brown patches, indicating papillary bumps. Brown spots on the arms are recommended to consult a doctor in a timely manner, and all of the above drugs should be used under the guidance of a doctor.