Darkening on both sides of the thighs may be due to physiological reasons such as prolonged friction, or it may be caused by diseases such as acanthosis nigricans and tinea cruris. You can take antibacterial drugs and antikeratinizing drugs under doctor’s guidance and advice, common ones are clotrimazole and Avicenna capsule, and acanthosis nigricans can also be treated by surgery. 1. Prolonged friction: thighs in a long time friction, stimulation, there will be pigmentation, will lead to thighs on both sides of the black symptoms, in the case of not affecting the normal life can not be treated. 2. Acanthosis nigricans: Acanthosis nigricans may be caused by obesity and malignant tumors, if it is caused by obesity and acanthosis nigricans, it is necessary to pay attention to weight control and then take antikeratinizing drugs, commonly known as Avicenna capsule, which will make the phenomenon of darkening of inner thighs subside slowly. If it is caused by malignant tumors, you must actively look for visceral tumors and carry out resection. 3. Ringworm: ringworm is a local skin disease of fungal infection, patients can use external clotrimazole, miconazole, etc., oral itraconazole, terbinafine and other drugs under the guidance and advice of the doctor for treatment. When the patient appeared thighs on both sides of the black symptoms, should be timely to the regular hospital, clear cause, follow the doctor’s advice, active treatment. The use of drugs need to follow the doctor’s instructions.