Acne is caused by a combination of hereditary predisposition (genetic factors) and stimulation of skin glands by male hormones.

Both men and women produce both male and female hormones, but men mainly produce male hormones and women mainly produce female hormones.

In the second half of the menstrual cycle, particularly as menstruation is approaching, there is a fall in the amount of estrogen (female hormone), although the small amount of male hormone remains more or less constant. This results in a relative increase in the influence of the small amount male hormone present. In the susceptible woman, this will lead to increased acne just before the menstrual flow.

BCPs are usually effective in treating this. In fact, BCPs are usually helpful in treating acne in general, primarily because of the suppression of ovarian function. Since the ovaries produce about a third of all male hormone in women, this drop in male hormone levels is often sufficient to lead to improvement in acne.

Occasionally, (uncommonly) the BCPs aggravate the acne, and in these cases, the BCPs should be switched or stopped altogether. If they are to be switched, good choices include those BCPs with strong, long half-life progestins, such as levonorgestrel.