Extra oil or sebum: There are oil glands on your chest, face and back numbering in the thousands. In fact, between the nose and cheek areas there are as many as two thousand oil glands every square inch. The function of these oil glands is to lubricate the skin by producing oil, or sebum. As the process advances, greater amounts of oil may be produced within the sebaceous glands, though the change in composition and quality of the oil may be more important than the quantity. The scale produced on the inside walls of the hair follicle becomes stickier, and it builds up and blocks the pore. This shows up as whiteheads and blackheads (comedones).
Bacteria: The acne bacteria as known “Propionobacterium acnes” that grow and multiply in the retained oil. The sebum acts as a nutrition source for the bacteria, which in turn releases chemicals within the pore. These alert and attract white cells from the blood, and that’s what leads to inflammation. On the skin, the inflammation is seen as pimples or zits.