Darkening of the elbow can be a symptom caused by physiological factors such as localized friction, but also by diseases such as psoriasis and acanthosis nigricans. Patients with black elbows should undergo general treatment, medication and physical therapy under the guidance of doctors. 1. Physiological factors: When the patient’s elbow is black in color, the skin is not thickened and there is no itching symptom, it may be a symptom caused by long-term friction. Patients can use hot towels to apply hot compresses on the affected area every day, and then use vitamin E or moisturizing lotion to smear the area of elbow, which may relieve the symptom of dark elbow. 2. Psoriasis: It is an inflammatory skin disease, which is manifested as inflammatory red papules in the early stage of the disease, and then it will gradually expand or merge to become brown plaques, which will lead to the symptom of black elbows in the elbow area. Patients can use topical mometasone furoate ointment, halometasone ointment and other glucocorticosteroid drugs or carbotriol ointment and other vitamin D3 derivatives. 3. Acanthosis nigricans: Acanthosis nigricans is mainly manifested as skin pigmentation, skin papillae and other symptoms. Patients can use topical medications such as retinoic acid gel, coal tar sulfate ointment, hydroquinone cream, etc. as well as oral compound vitamin A and other medications. Patients can also use laser, electrocautery and other physical treatment methods. Patients need to note that if physiologic causes are excluded, they should seek medical attention and be treated accordingly under a doctor’s diagnosis.