The skin on the hand is coffee-colored, it may be physiological hyperpigmentation or pathological disease, commonly caused by phimosis, it is recommended to visit the dermatology department of the hospital to clarify the cause of the disease in order to treat the cause. 1, physiological factors: hyperpigmentation is due to sun exposure, ultraviolet radiation, drugs and other factors, resulting in uneven deposition of melanin in the skin and the formation of the phenomenon of skin color deepening. Clinically, you can use cumene cream ointment to reduce the scope of hyperpigmentation, or use fractional laser to improve the symptoms of hyperpigmentation, while paying attention to the prevention of triggering factors, pay attention to sun protection, you can avoid ultraviolet radiation by wearing sunscreen; 2, pathological factors: mosaic moss is commonly known as sweat spot, is caused by the fungal dermatitis of Sphaerococcus furfuraceus, can form a soybean-sized dark brown or brown rash, the skin surface will have chaff The skin surface will have bran-like phosphorous flakes. Clinically, antifungal drugs are generally used, such as fluconazole dispersible tablets, itraconazole capsules, etc.; 3, other factors: if the trace elements are oversupplemented, certain symptoms can appear, such as excessive iron supplementation, causing a large amount of iron deposition in the body, pigmentation can occur. Therefore, you need to pay attention to the appropriate amount of iron supplementation, do not exceed 18mg per day. daily life should pay attention to the cleanliness of the skin on the hands, while paying attention to sun protection, can prevent the above symptoms to a certain extent.