When darkness appears on the back and waist, the skin pattern of the darkened area needs to be carefully observed. If the texture of the skin is the same as normal skin to the touch, it is possible that the blackening is mainly due to the color of the skin. This condition is associated with long-term exposure to tar, asphalt or working in an environment with irritating gases, and can be treated by getting out of this environment and then taking oral glutathione. If there is significant keratosis with significant itching in the blackened area of the back, it may be considered chronic keratotic dermatitis, which is directly related to long-term friction, irritation, allergy and other factors, and it is recommended to use compound lactic acid cream with hydrocortisone butyrate cream for treatment. If there is significant pain in the skin of the blackened area, consider the possibility of subcutaneous bruising suggest the choice of hot towels for hot compresses.