The usual forehead darkening, often refers to the forehead area of the skin color is darker than other parts of the face. The black forehead to distinguish the black may be due to daily rest, sleep is not good, and often stay up late caused by, for this kind of forehead black just pay attention to adjust the rest can. In addition, the forehead darkening may also be some people often contact sun exposure work caused by the sun is too strong, ultraviolet light can stimulate melanocytes to increase, so the forehead area of the darker skin tone. For this reason caused by dark skin tone is recommended to avoid sun exposure, when working outside can apply sunscreen locally. There are also pathological reasons, some people may have darker skin tone due to liver and kidney diseases. For forehead darkness caused by disease, it is recommended to seek consultation and treatment from the relevant specialist at the hospital.