Our skin glows most when the dominant hormone is estrogen: It keeps things firm, plump, and smooth by increasing collagen, the building block of skin. Not to mention hydrated (by stimulating hyaluronic acid, which attracts water molecules) and pimple-free (by lowering oil gland activity and tamping down inflammation). But when estrogen declines—during the week of your period, as you age and as menopause approaches—you can still take steps to help skin smooth out, firm up, and glow on. Here’s how.  In Your 20sHow your hormones are changing:The Venus Week Estrogen peaks during your 20s, giving most women their best-ever complexion: luminous, taut, and even-toned. The shift in hormone levels around your period, however, can lead to acne. Throughout the month, estrogen masks the sebum-producing effects of testosterone, but when estrogen dips the week leading up to your period, newly dominant testosterone makes its presence known in the form of breakouts and blemishes, explains Rebecca Booth, MD, ob/gyn and author of and cofounder of VENeffect Anti-Aging Skincare.   What it looks like: More oil production, larger pores, and breakouts along the jaw line during your period. “The wild swing of hormones can be inflammatory, causing deep, painful zits called cysts,” says Tanzi. And for some women, this can happen during any time of the month. “Even women who have never had a pimple could have early onset of adult acne at this age,” she adds. Treat it: Regulate hormones causing chronic acne by getting a prescription for birth control pills, which balance hormone levels, or medications such as Spironolactone and Aldactone, which counteract the effect of male sex hormones on the skin. “These drugs help block some of the testosterone receptors, shifting hormones so oil production and acne diminish,” says Rachel Nazarian, MD, assistant clinical professor of dermatology at Mount Sinai Hospital in New York City. For occasional breakouts, Tanzi recommends applying an acne mask with salicylic acid 2 to 3 times a week, and using spot treatments as needed. We like Clean & Clear Blackhead Eraser Cleansing Mask ($6, walgreens.com), which has 0.5% salicylic acid and Receutics Active Skin Repair Breakout Treatment ($20, receutics.com), which clears skin with a 3.4% dose of benzoyl peroxide.  MORE: 7 DIY Skin-Care Recipes Facialists Use On Themselves In Your 30sHow your hormones are changing: This is when estrogen levels start to dip, heralding sinking levels of skin-tightening collagen and elastin and skin-plumping hyaluronic acid. Cell turnover slows, too, and skin bounces back less easily from inflammation. Dryness and acne are likely to show up during this decade, too, says Tanzi.  What it looks like: Dryer, thinner skin, more obvious traces of expression lines on the forehead and around the eyes, the beginnings of age spots, and an increased flaring of inflammatory conditions like rosacea and occasional acne.   Treat it: Ramp up your anti-aging skin regimen, especially at night when skin naturally rests and repairs. Nazarian recommends adding a product containing retinol, a vitamin A derivative that thickens skin by increasing collagen production to smooth wrinkles and reverse volume loss. Try Roc Retinol Correxion Sensitive Night Cream ($23; rocskincare.com) or Neutrogena Rapid Wrinkle Repair Serum ($22; neutrogena.com), which are gentle enough for first-time users. MORE: 9 Gross Beauty Habits That Aren’t Doing You Any Favors In your 40sHow your hormones are changing: So long, estrogen. During this decade, expect less firmness, elasticity, and moisture. According to Nazarian, estrogen-related bone loss can start to affect your facial structure, too, leaving you with sunken-looking eyes and slackening skin. What it looks like: Significant drying, dulling, hollowing, and more visible wrinkles, capillaries, broken blood vessels, and age spots. “Patients tell me, ‘my skin changed overnight!’ " Tanzi says. “I used to think it was an exaggeration, but it isn’t—there are dramatic changes in the 40s, especially when it comes to loss of elasticity.”  Treat it: If you have crazy-heavy periods and hot flashes, Diana Bitner, MD, an ob/gyn at Spectrum Health Medical Group in Grand Rapids, Michigan recommends birth control pills or Mirena, an IUD with progesterone, plus a low-dose estrogen patch just during the week before your period to even out your hormones. Healthy lifestyle choices, like staying hydrated, getting adequate sleep, eating a balanced whole foods diet low in sugar, and exercising, will help improve your look, too.  Extra steps: In addition to a good at-home skincare regimen—a gentle cleanser, moisturizer, serum, eye cream, and SPF daily on your face, neck, and chest—it’s time to upgrade to a prescription retinol like retinoic acid or Retin-A, or move up in concentration, from .025%, for example, to .03%. “Retinol reminds skin cells to behave as they did when they were young and healthy—it minimizes wrinkles, thickens skin, controls acne, strengthens blood vessels (so there’s less breakage and discoloration), and fades sun spots,” Nazarian says.  Boston dermatologist Ranella Hirsch, MD, says it’s also the perfect time to incorporate phytoestrogens (plant compounds such as soy, genistein, grape seed, green tea, and wild yam) into your routine. They prevent sagging by mimicking estrogen’s collagen-restoring effects on the skin, says Booth. And they’re safe to use because they stay local and don’t spread to the body, Booth confirms. Check product ingredient lists for the plant compounds listed above, or try VENeffect’s Firming Phyto-Lift Serum ($195, veneffect.com). MORE: 5 Ingredients To Avoid If You Have Dry Skin In your 50s and beyondHow your hormones are changing: Estrogen sputters to a halt during menopause (which happens around age 51 or 52 for most), and testosterone takes center stage. You’ll lose a third of your collagen within the first five years of menopause, and with it your skin’s bounce-back, moisture and glow, Bitner says. Inflammation also peaks, making skin more vulnerable to skin damage from sun, smoke, and pollution. (Sleep better, balance your hormones, and finally lose weight with the The Hormone Reset Diet!) What it looks like: Skin thins, dries, deflates and gets looser. Lines become deeper, pores stretch, lids may sag and become hooded, eye sockets hollow, spider veins may become more visible, age spots show up, and small-yet-benign bumps, patches, or skin tags may grow. Expect peach fuzz, if you didn’t already have it, on the cheeks, chin, and upper lip. Treat it: Hormone therapy, where estrogen levels are raised just high enough to alleviate symptoms, is a safe option for many women, Bitner says. Skincare-wise, it’s time to hydrate, hydrate, hydrate, because without the natural hyaluronic acid that comes with estrogen, skin doesn’t hold onto moisture. “My patients in this age range complain that their skin is literally cracking from dryness,” Nazarian says. Ditch harsh soaps, lower the temperature of your showers, and wash your face only at night to avoid endangering the already-low levels of hydration in your skin. Choose a product with hyaluronic acid, redness-reducing niacinamide, and skin barrier-supporting ceramides. Try CeraVe Skin Renewing Night Cream, which contains all three ($17, ulta.com). Extra steps: To really turn back the clock, see a dermatologist for injectables, lasers, or radio-frequency or ultrasound treatments. A few possibilities: Botox and Dysport injections to smooth lines, fillers like Juvéderm XC, Juvéderm Voluma, Belotero, and Radiesse to fill in deeper grooves and replace lost plumpness, and Restylane injections to camouflage dark circles (take a look at this ultimate guide to injectables if you’re going to go that route). Lasers like the Clear + Brilliant Perméa will erase brown spots, while others, such as the new Smoothbeam, can help clear acne. Finally, radio-frequency technology Thermage, and ultrasound wave procedure Ultherapy can tighten skin in areas like the brow, neck, and chest.