Painful bumps on the back can be caused by boils and sebaceous cysts. 1. Boils: When the skin on the back is scratched or abraded, bacteria will invade through the pores of the hair follicles and boils will occur, manifesting themselves as red, hemispherical and painful bumps on the surface of the skin, with pus in the center of the bumps, which will get bigger and bigger and become more and more painful with the development of the disease, and will discharge pus when it ruptures, after which the pain, redness and swelling will be gradually reduced. 2. Sebaceous cysts: when the sebaceous gland ducts are blocked, due to poor sebum excretion and retention of sebum piled up together to form cysts, it will cause the back of the long pimples, if the subsequent secondary infection, there will also be pain. There may also be other causes for the pain of long flesh bumps on the back, so it is recommended to go to the hospital in time to improve the examination and give targeted treatment after clarifying the cause of the disease.