Hard black seeds on the back can be considered as blackhead pimples, epidermal cysts, melanocytic nevi, etc. 1. Blackheads: If the hard black seeds on the patient’s back appear as conical pimples, with larger inflammatory pimples, nodules and pustules after secondary infection, then it can be considered as blackheads; this disease is usually caused by keratinization of the sebaceous gland opening of the hair follicle and narrowing of the opening leading to the follicle sebum is not easy to exclude, clogging, and after a long period of oxidation, it turns into a black and hard particles. 2. Epidermoid cysts: If the black hard seeds on the patient’s back appear as dome-shaped elevated skin swellings, with the diameter of the cysts ranging from several millimeters to several centimeters, developing slowly, hard, skin-colored or brownish-blue, with the center being black, then it can be considered to be epidermoid cysts; 3. Melanocytic nevus: the black hard seed-like lesions on the patient’s back may also be melanocytic nevus, which belongs to benign skin tumors of melanocyte origin; this disease is caused by melanocytes gathering in nests, and the main function of melanocytes is to produce melanin so as to change the color of the skin, which often manifests multiple, morphologically varied spots, papules, and so on. It is recommended that patients go to regular hospitals in a timely manner, under the guidance of a professional doctor, conduct relevant examinations, clarify the cause of the disease, and then follow the doctor’s instructions to receive treatment.