A lot of small black spots on the back may be caused by blackheads and acne, hyperpigmentation after inflammation subsides. 1. Blackheads: Due to the abundance of sebaceous glands on the back, if the sebaceous glands secrete exuberantly and the keratinization of hair follicle openings is abnormal, so that excessive sebum cannot be discharged in a timely manner at the mouth of the hair follicle, the mouth of the hair follicle can be blocked, and the part that is exposed to the air oxidizes to form small black dots. 2. Hyperpigmentation after inflammation subsides: it is usually related to infection, such as the local skin on the back is infected by Malassezia, which can induce florid chaff rash. After the lesions gradually subside, pigmentation can be formed in the affected area, appearing black spots on the back. It is recommended to go to the hospital in time to clarify the cause of the disease and carry out targeted treatment under the guidance of the doctor. Pay attention to keep the back skin clean and hygienic, usually choose loose, comfortable, breathable clothes.