The statement that darkening of the skin on the lower back alerts to four diseases is not true. For example, clothing staining, subcutaneous bleeding, long-term friction, sun exposure and other factors may also lead to local color blackening. 1. Clothing material staining: new clothes if the color loss is more powerful, clothing long-term friction with the waist skin, may lead to the waist black. 2. Subcutaneous hemorrhage: the waist is subjected to external forces leading to subcutaneous hemorrhage, dark brown patches may appear on the skin. 3. Friction, sun exposure: waist long-term friction, usually do not pay attention to sun protection, ultraviolet radiation, may lead to subcutaneous pigmentation, black color. To sum up, the color of the skin of the waist is darker, not necessarily caused by disease. It can also be considered to be related to the staining of clothing, the effect of external forces and other factors. If you suspect that it is caused by pathological factors, it is recommended to go to the hospital to look for the cause and treat it with the doctor’s advice.