The difference between chloasma and brownish blue nevus is different onset causes, different colors and different distribution ranges. 1. Different causes: chloasma is related to heredity, but there are some other triggering factors, such as ultraviolet radiation, changes in the level of sex hormones, etc., and it usually develops in the middle age. Melasma is mainly a genetic factor, belonging to chromosomal dominant inheritance, and most of this disease is present at birth. 2. Different colors: Melasma is mainly light brown or dark brown spots or patches with clear boundaries and irregular shapes, which is reduced in winter and aggravated in summer. Brownish blue nevus is usually grayish blue, greenish gray, grayish brown, etc., the boundary is not clear, and the color will usually deepen with age. 3. Different distribution ranges: Melasma usually occurs in the prominent parts of cheekbones, and may also be on the forehead, upper lip, nose and jaw. Melasma mainly occurs on one side of the face, which is more common in the parts innervated by the first and second branches of trigeminal nerve. If you cannot distinguish between chloasma or brownish-bronze nevus, it is recommended to go to a regular hospital to be identified by a specialist, and if abnormal symptoms appear, it is recommended to consult a doctor in time.