Usually, if the patient has blackened thigh roots, there are several cases as follows: 1, melanosis, because the inner thighs are not easily exposed to external sunlight for a long time, at this time, there will be melanosis, which will lead to blackening of the thigh roots. The color of this melanin deposition is not particularly deep, and usually does not cause any health effects and threats. 2, if the root of the thigh is very serious black, you need to check the endocrine function. The actual blackening of the thighs is usually due to the relatively high accumulation of subcutaneous fat and the friction between the two sides of the thighs, and the epidermis after the friction has been agitated and proliferated, which will lead to the blackening of the situation.