Black elbows and knees may be caused by melanin deposition, limited dermatitis, etc. Treatment should be chosen according to different causes, such as reducing friction and medication. 1. Melanin deposition: frequent friction will lead to melanin deposition, should choose soft skin-friendly clothing, reduce the friction on the elbows, knees, elbows and knees to alleviate the phenomenon of black phenomenon, you can also choose to use Vitamin A acid ointment, salicylic acid ointment and other medications coated in the elbows and knees, reduce the roughness phenomenon. 2. Restricted dermatitis: the skin of patients with restricted dermatitis can be mossy, manifested as black skin. Patients can use mometasone furoate cream to apply, or oral antihistamine drugs, such as loratadine. If the elbows and knees are black, it is recommended that the patient should consult the hospital in time to clarify the cause of the disease and then carry out targeted treatment.