• How hormones cause acne: Hormones or androgens, like testosterone, stimulate the sebaceous glands that create oil. They start producing excess sebum, an oily substance found naturally in the skin. When sebum mixes with bacteria or dead skin cells and becomes trapped inside the pores, acne develops. Not surprisingly, the emergence of acne usually coincides with the onset of puberty and menstruation, when hormone levels soar.

  According to endocrinologist Geoffrey Redmond, M.D., of The Hormone Center of New York, doctors can perform tests to determine if your hormones are at appropriate levels. He notes that some women might even have a hormonal disorder, which can explain their acne.

• How the pill helps: Birth control pills counteract these oil-producing androgen effects. They contain hormones, such as progestin and estrogen, which reduce androgen levels. This causes a domino effect: With lowered androgen levels, skin has less oil production and fewer clogged pores, which results in a clearer complexion. The bad news? Acne and other skin irritations can return after you discontinue the pill.

Step 1: Cleanse and tone

Opt for a cleanser to remove excess oil, bacteria and makeup without being too harsh or drying. Avoid soaps and cleansers with heavy fragrances, which can be irritating. Don’t cleanse more than twice a day or scrub your skin, because cleansing too often and too hard can worsen acne, according to the American Academy of Dermatology. Make sure to rinse well. Then, follow with a gentle toner containing witch hazel to wipe off any remaining residue and control oil production, suggests Melissa Kagan for iVillage.

• La Roche Posay Effaclar Foaming Purifying Gel deep cleans to get rid of acne-causing oil and grime while still being gentle on your skin.

• SkinMedica Rejuventaive Toner, which contains witch hazel and other botanical ingredients, banishes excess oil and helps pores appear smaller.

Step 2: Exfoliate

Exfoliation is essential for women with acne, because it removes dead skin cells that can clog pores. Facial peels and scrubs are effective exfoliants. While the peel is on your face, you might experience some itchiness or irritation, but it should subside quickly. Discontinue use and call your dermatologist if it doesn’t go away after a day.

• Philosophy Microdelivery Facial Peel exfoliates dead, dry skin and restores your natural radiance.

• Cellex-C Speed Peel Facial Gel sloughs off dead cells without irritation, revealing smooth, healthy skin.

• Avene Gentle Purifying Scrub gently exfoliates the skin, keeps pores clear and reduces inflammation.

  Keep in mind that exfoliating too frequently can irritate the skin and exacerbate acne. Limit exfoliation to once or twice a week. If your skin feels irritated, exfoliate less often.

Step 3: Choose oil-free moisturizers

An oil-free, noncomedogenic moisturizer is one of the most important skincare items for women with acne. This type of moisturizer hydrates skin without clogging pores, adding unnecessary oils or making skin feel greasy.

• Peter Thomas Roth Oil-Free Moisturizer is rich in antioxidants and vitamins. This formula hydrates the skin, making it feel baby soft.

• Bliss Oil-Free Sunban Lotion for the Face SPF 30 moisturizes skin and protects against aging and sun damage with vitamins C and E. Unlike many moisturizers, this product is oil-free, lightweight and non-greasy.

Step 4: Spot treat blemishes

When acne occurs, it must be treated instantly. You want a product to clear up your acne without causing dryness or irritation. Luckily, plenty of options fit the bill.

• Murad Acne Spot Treatment reduces redness and blotchiness. Containing salicylic acid, this product gently exfoliates the skin, leaving it protected and ready to start anew. Hydrolyzed oat flour and zinc oxide prevent dryness, flaking, irritation and other unpleasant side effects.

• Neutrogena On-the-Spot Acne Treatment features 2.5 percent benzoyl peroxide, which is gentler and less drying than higher concentrations of benzoyl peroxide (typically more effective for teenage skin). But it’s still as effective in killing acne-causing bacteria and keeping pores clear.

Step 5: See your dermatologist

If all else fails and you’re still seeing pimples pop up, head to your dermatologist for other treatments. But be aware that some treatments may not be right for you if you’ve stopped taking birth control pills to get pregnant or if you’re currently nursing.

• Oral and topical prescriptions: antibiotics, retinoids or isotretinoin (Accutane).

• Procedures: phototherapy with special lights, microdermabrasion or surgery to correct acne scarring.

Learn everything you need to know about acne-fighting skincare in our Complete Acne Handbook.