Back squeeze out black hard things may be blackhead acne or sebaceous cysts and other black keratin plugs formed, generally in the sebum overflow more occurs. Back skin sebaceous gland secretion is more, when the pore is epidermal cells dander block, sebaceous gland oil can not be discharged, keratinized epidermal cells, sebum and dust, etc., mixed, contact with the outside air oxidation can be formed blackheads acne, in the follicle mouth to form the tip of the black or brown keratin plug. If the sebum in the hair follicle is retained for a long time when the discharge is blocked, a large amount of secretion is gathered in the cystic cavity, thus becoming a sebaceous cyst, and there is a black hard keratin plug at the opening of the cyst. It is recommended that when pimples or bumps appear on the body parts, avoid squeezing with hands to prevent infection and seek medical help and treatment in time.