Men with dark itching on both sides of the thighs may be related to physiological factors such as dry skin and friction, or it may be caused by eczema, ringworm and other diseases. 1. Physiological factors: If the skin is too dry, it may lead to local skin peeling and itching. In addition, when men walk, the local skin and clothing will be friction, long-term may make the local black. 2. Eczema: its cause may be genetic, environmental, disease and other factors, patients will appear red spots, pimples and itching. After the lesions heal, localized pigmentation may occur, resulting in localized blackening. 3. ringworm: its cause is mostly related to the skin ringworm infection, sweating, low immunity may also induce the disease. Patients will appear erythema, papules and itching symptoms, due to inflammation stimulation, can also lead to melanin deposition. The causes of black itching on both sides of the thighs in men are not unique, and after ruling out physiological factors, patients are advised to seek medical examination to clarify the cause of the disease.