Sebum normally flows up to the skin surface through hair follicles. Acne occurs when the path of sebum is blocked, usually by dead skin cells mixed with sebum. The hormones that have the greatest effect on the sebaceous glands are the male hormones called androgens. Both women and men carry male hormones, of course, in different quantities. Your hormones also affect the way your skin grows and sheds dead cells during this time of your life-they can stick together and clog your pores.
Sebum builds up in the follicle, becomes infected leading to the basic acne pimple.
Inflammation can then spread to surrounding parts of the skin. The result is a large and painful lump under the skin called an acne nodule. Acne nodules often leave scars when they heal. Contrary to what you may have heard, greasy foods and foods in general do not cause acne, neither does poor hygiene. Scrubbing with cleansers or a harsh cloth is not likely to clear it up and may actually worsen it.