More arm spots may be caused by pigmented nevi, age spots, freckles, vitiligo and other diseases. 1. Pigmented nevus: belonging to benign neoplasm of skin, it is a common clinical benign tumor of skin, which can lead to the appearance of skin surface hyperplasia with different colors, sizes and morphologies, and is mainly manifested as mottled rashes, papules, nodules, and so on. 2. Age spots: also called seborrheic keratosis, are benign intraepidermal tumors, mostly seen in the elderly. The lesions are common in scalp, face, trunk, upper limbs, etc. In the early stage, there may be patchy manifestations, and with the progress of the disease, the patches are gradually enlarged. 3. Freckles: the causes of freckles mainly include heredity and sun exposure, and heredity is the main cause of freckles. The patient’s face, especially the nose and cheeks, sometimes involving the shoulders, arms and other parts of the body, can lead to localized hyperpigmentation spots. 4. Vitiligo: white is a skin and mucous membrane pigmentation disorder, can occur in any part of the body, especially sunlight, easy to friction, exposed parts, resulting in local white spots. In addition to this, sun spots, post-inflammatory pigmentation, etc. can also lead to spots on the back of the hand. It is recommended to go to the hospital in time to clarify the cause of the disease and follow the doctor’s instructions to standardize the treatment.