Ovulation occurs about two weeks before your period arrives, or roughly 14 days into a typical 28-day cycle. This is when a wee egg, called an ovum, leaves your ovary and makes its trek to your uterus via a fallopian tube. The continued increase in estrogen levels during this time triggers an increase in a different hormone, referred to as Luteinizing hormone (LH).Unfortunately, LH increases oil production, which breeds the ideal environment for bacteria and, you guessed it, acne. You're likely to see a blemish or two appear during these days in your cycle, so this is prime time to really amp up your anti-acne routine and tend to your skin as best as you can."During the oily times, make sure to use an oil-free makeup and oil-free moisturizer," says Michele Green , MD, a board certified dermatologist and contributor at RealSelf.com. She says to look for the words "non-comedogenic" when buying and using skin-care products, as they have been tested and do not clog your pores or cause acne.Once your egg adheres itself to the now-cushy walls of your womb, it sits and waits for a sperm to join the party. But when fertilization doesn't happen, your level of estrogen will decrease, which initiates good ol' PMS as your uterus preps for a shedding extravaganza."Skin tends to look its worst during the days leading up to your period," says Dr. Palmer. "There is a decrease in estrogen and surge of progesterone and testosterone about a week before your period. This surge can cause oil production and pores to become clogged with sebum, making them appear larger."Welcome to breakout city. “These breakouts can be anywhere on the face, but typically hormonal acne tends to be on the chin and along the jawline,” notes Dr. Green. Sounds familiar.Dr. Palmer recommends using a cleanser with a higher amount of salicylic acid during the blemish-prone period that is PMS. This type of cleanser cleans out pores more effectively, nixes excess oil, and keeps bacteria and blemishes at bay."I always recommend using a retinoid because it will not only even out your pigmentation, but will also reduce your risk for breakouts and give a smoother texture to the skin," adds Ava Shamban , MD, a board certified dermatologist and founder of AvaMD.As you may have guessed — or surmised from your own experience over the years — this is the portion of your cycle where your skin is most sensitive. For this reason, it's particularly imperative that you're attentive to its needs.