The appearance of blackening on both sides of the buttocks requires careful observation of the skin appearance of the blackened area. If the color is simply blackened and there is no obvious change, it is considered a normal phenomenon. Because simple pigmentation of the skin on the buttocks formed by long-term walking and friction will not affect the body, it can be ignored and hydroquinone cream can be applied for whitening. If there is mild keratinization on both sides of the blackened area, distributed on both sides of the lower edge of the sciatic bone, it is considered to be related to long-term sitting and formed after prolonged skin extrusion and friction, so you can choose to use compound lactic acid cream or salicylic acid cream to soften the skin and achieve the purpose of restoring white and tender. If both sides of the buttocks and the roots of the thighs are blackened, and the blackened skin is raised at the edges and sunken in the middle, with strong itching, it is considered to be ringworm formed after fungal infection, and a fungal test can be done to clarify the diagnosis.