Acne is basically an inflammation of the skin, and more severe inflammation may leave marks on the face. This includes melanin deposits, red spots, hollows or raised scars. 1, poor sebaceous gland secretion: If infection is the main factor in acne scar formation, then poor sebaceous gland secretion is the physiological basis for the formation of infection. 2, squeeze the sebaceous glands secondary infection: When papules appear, patients often subconsciously use their hands to squeeze. The actual fact is that the actual skin is often damaged due to the incorrect squeezing method, and the barrier protection function of the skin is reduced, plus the sebaceous gland contents are not thoroughly squeezed out, and bacteria take advantage of the situation. Inflammation of the sebaceous glands can occur secondary to this. As many patients ignore the importance of treatment. In the lumen of the sebaceous gland, tissue repair and destruction coexist, resulting in the formation of keloids, keloid scars, atrophic keloids, and uneven keloids. This is an important part of acne scar formation. 3, improper treatment: When the sebaceous glands enter the inflammatory phase, many patients often do not pay enough attention to the treatment, some treatment stop. This results in repeated local inflammation, serious destruction of the duct cavity, and even skin epidermalization, resulting in closure of the duct cavity, and after healing, epidermal depressions and dermal adhesions, forming depressed keloid scars the size of green beans.