Dense small black spots on the back may be caused by follicular keratosis pilaris and blackheads, which can be relieved by medications such as retinoic acid cream and fusidic acid cream. 1. Follicular keratosis pilaris: Follicular keratosis pilaris is caused by the expansion of the funnel part of the hair follicle due to over-keratinization and embolization by keratin, manifesting itself in the form of pinpoint-sized keratotic pimples on the surface of the skin in the form of small black dots. Local topical keratolytic agents, such as vitamin A acid cream, urea ointment, salicylic acid ointment, etc., severe symptoms can be combined with the application of oral medications, such as vitamin A, vitamin C, vitamin E, etc. to reduce the symptoms. 2. Blackheads: Blackheads are caused by abnormalities in the local development of hair follicles, mainly manifested as clusters of blackheads and acne-like pimples, occurring on the face, chest and back. Local topical acne solving drugs, such as Vitamin A acid cream, and topical anti-microbial drugs, such as fusidic acid cream, benzoyl peroxide preparation, etc.; if secondary infection, oral antibiotics, such as roxithromycin capsule, tetracycline capsule, etc.. All of the above drugs need to be used under the guidance of a professional doctor to avoid self-medication. Dense black dots on the back may also have other causes (such as small spiny moss), it is recommended to go to the hospital in a timely manner to improve the examination, to clarify the cause of the disease and then give targeted treatment.