Black skin on the back near the spine is considered to be post-inflammatory hyperpigmentation, acanthosis nigricans and birthmarks. 1. Post-inflammatory hyperpigmentation: If eczema, dermatitis and other skin diseases have occurred in the area of the back near the spine before, the pigmentation will be left behind after the recovery of the condition with medication, which will be manifested as darkening of the skin. 2. Acanthosis nigricans: the etiology and pathogenesis of acanthosis nigricans is still unclear, considering heredity, obesity, tumors and other factors, mainly manifested as skin pigmentation and skin papillae. 3. Birthmarks: birthmarks are abnormal proliferation of skin tissues during development, manifested as abnormalities in the shape and color of the skin, most of which are present at birth, and may also appear slowly in adulthood. Back near the spine skin black may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.