Why do some people get acne and others do not?

It is not clear why some people are more prone to acne than others. The exact cause of acne is not known, but one important factor is an increase in male sex hormones called androgens. Androgens increase in both boys and girls during puberty. Androgens cause the sebaceous glands (oil glands) to get larger and produce more sebum. Androgens also can increase because of hormonal changes related to pregnancy or starting or stopping birth control pills.
Another factor in the cause of acne is genetics. Researchers believe that the tendency to develop acne can be inherited from parents. In addition, some drugs (for example, anti-epilepsy medication, prednisone, androgens and lithium) are known to cause acne. Cosmetics that have a greasy consistency may change the cells of the follicles, causing them to stick together and resulting in a plugged pore. Water-based products are less likely to cause acne.
Things that can make acne worse include:
Friction caused by leaning on or rubbing the skin; harsh scrubbing
Picking or squeezing blemishes
Pressure from bike helmets, backpacks, or tight collars
Changing hormone levels in adolescent girls and adult women two to seven days before the start of the menstrual period
Stress
Other factors that were previously thought to make acne worse do not seem to have an effect on the development of acne. These factors include chocolate, greasy foods, and dirty skin. click here for total treatment.