Hormones called androgens overstimulate the skin's oil glands, which frequently leads to a breakout around menstruation. (If you break out along your jawline, this is likely the culprit.) Some women find relief by going on oral contraceptives — aka the pill — but you'll need to discuss the benefits and risks with your doctor.
Acne Culprit: It's That Time of the Month
Source: Flickr user GorillaSushi