What you need to know to save your skin

Dull skin
The cause: You may still be running marathons, but your skin cells are already losing steam by around age 30. "Cell turnover starts to slow down around this age, which leads to a buildup of dead skin, and it doesn't always slow at the same pace across your face," says Wechsler. "So you end up with patches of dead skin in some areas, causing your complexion to be dull, uneven, and rough."

The treatment: Exfoliate once a week to remove the top layer of dead cells and reveal the fresh skin underneath. Doctors prefer at-home alpha hydroxy acid (AHA) or salicylic acid peels over scrubs. "People tend to rub harshly in certain areas which can cause uneven exfoliation and irritation," says Alster. "A peel provides an even layer of product across the face to chemically loosen dead cells." Don't leave a peel on for longer than the instructions advise, and be sure to moisturize afterward. If you have sensitive skin, test the product first on a small patch of skin in front of your ear, says Wechsler. MD Formulations Daily Peel Pads (with salicylic acid) and Juice Beauty Green Apple Peel Sensitive Pads (with AHAs) make it easy to exfoliate in one quick swipe. To force your skin into the habit of faster cell turnover, introduce products containing ingredients that speed up the process into your regimen. Try a mild salicylic acid cleanser, such as Dermalogica Clearing Skin Wash, or a cream with either alpha hydroxy acid or retinol (we like Neutrogena Healthy Skin Face Lotion SPF 15 or Remergent Retinol Therapy) — just don't use the creams within an hour of the salicylic cleanser or the AHA peel to avoid irritating skin (by doubling up on AHAs) or negating the effects (salicylic acid and AHAs can lessen the effectiveness of retinol).

Hyper-pigmentation
The cause: Hyperpigmentation is the clinical term for brown spots, freckles, and dark patches — all caused by an overproduction of melanin. Sun damage is typically to blame for small, individual brown spots, while a rise in estrogen levels in your body — often brought on by pregnancy or certain types of birth control pills — causes larger, irregular splotches of dark skin known as melasma.

The treatment: The only over-the-counter ingredient strong enough to actually bleach skin is hydroquinone — "It can get rid of a dark spot or melasma entirely," says Wechsler. There has been controversy over the ingredient because of some patients who used it in extremely high concentrations and developed darker spots, but as of now, "it remains the best treatment for hyperpigmentation," says Wechsler. (You can find it over the counter in Murad Age Spot & Pigment Lightening Gel.) In addition, because AHAs and retinol help speed up cell turnover, they prompt skin to shed the darker cells while also evening out melanin production so you don't get clusters of pigment. (Try Dr. Michelle Copeland AHA Face Cream or L'Oréal Advanced Revitalift Night Cream.)

It takes four to eight weeks for a lightening agent to completely fade a dark area of skin, and brown spots and melasma are notorious for recurring. "Patients will tell me that the bleaching creams don't work, and then I'll find out they're not wearing sunscreen," says Fredric Brandt, a cosmetic dermatologist in New York City and Miami. "Unless you apply a broad-spectrum sunscreen every day and avoid prolonged sun exposure, the treatments aren't going to work."

Dryness
The cause: Oil is in overdrive when you're a teenager, then it nearly runs dry as you get older. "Your skin gets about 10 percent drier every decade," says Bank. While oil production decreases, the lipid barrier of skin, which traps and holds in moisture, becomes increasingly defective over time. "You've got a double whammy of less moisture production and less ability to hold moisture in the skin," says Bank.

The treatment: You need a good moisturizer, but a thick, rich cream could clog your pores when you're young. "Your moisturizer should sink in quickly but leave skin feeling supple," says Bank. Try a lightweight moisturizer with ceramides (which help build up the lipid barrier), such as Elizabeth Arden Ceramide Plump PerfectMoisture Cream SPF 30 or CeraVe Moisturizing Lotion. If your skin still feels dry, begin next time with a hydrating serum such as Vichy Aqualia Thermal Serum or Bioelements x10, then apply your moisturizer. If your skin feels tight after you wash it, "that means you've stripped it of all its natural, protective oils," says Wechsler. Switch to a cream cleanser — try Lancome Glatee Comfort. And be sure to exfoliate weekly with a chemical peel (it's gentler on dry skin than a scrub) — clearing away dead cells helps your moisturizer penetrate better. (Try Avon Anew Clinical Advanced Retexturizing Peel.)

Weathered neck and décolletage
The cause: Call it the forgotten territory. Even those who diligently apply sunscreen to their face often forget their neck and chest — and because the skin there is thinner and has fewer oil glands than the face, it's particularly susceptible to early signs of aging such as horizontal neck lines and brown chest spots. And once again, blame it on the sun.

The treatment: The same ingredients you use to treat lines and dark spots on your face will work on your neck and chest — but because the skin here is thin, it's more sensitive. To minimize irritation, apply your face cream to your neck and chest just two or three times a week. If you're particularly sensitive, use a neck cream — it typically has a lower concentration of active ingredients, such as retinols and lightening agents, than face creams. (We like Cellex-C Advanced C Neck Firming Cream.) And we may sound like a broken record here, but a broad-spectrum sunscreen applied daily to this area — even in the wintertime — is your best defense against further damage.

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