The darkening of the back of the hand may be physiological factors, but can also be considered related to post-inflammatory hyperpigmentation, seborrheic keratosis, warts and other factors. 1. Physiological factors: usually do not pay attention to sunscreen, often in the external environment, subject to ultraviolet radiation, the skin exposed parts of the phenomenon of photoaging, which may lead to black color. 2. Post-inflammatory hyperpigmentation: The skin on the back of the hand has previously experienced eczema, dermatitis and other skin damage, poor local blood circulation, chemical stimulation, usually do not pay attention to sunscreen, post-inflammatory hyperpigmentation may be left behind, resulting in black color. 3. Seborrheic keratosis: the cause of seborrheic keratosis is not yet completely clear, and it is considered to be related to age, heredity, sun exposure and other factors. If the hands are often exposed to sunlight, it may lead to localized brown patches or plaques. 4. warts: due to the skin of the hand infected with human papilloma virus and the occurrence of benign growths, will also appear on the back of the hand skin blackening. The back of the hand skin black, but also to understand the accompanying symptoms, if necessary, to the hospital dermatology, first clear cause, and then targeted to give treatment.