Q: Once and for all, do I need to modify my skincare routine when the weather turns cold?

A: Once and for all, yes, says Debra Jaliman, MD, clinical assistant professor of dermatology at Mount Sinai School of Medicine in New York City. Replace your exfoliating or heavily sudsing cleanser—both of which help reduce the extra sebum your skin produces in the humid summer months—with a milder, nonsudsing cleanser that can be used with or without water (without if you have extremely sensitive or eczema-prone skin). Many of these cleansers contain moisturizing glycerin, says Jaliman. She likes CeraVe Hydrating Cleanser, $12, and Dove Pro-age Foaming Facial Cleanser, $5. If you have normal or dry skin, it's probably best to skip a toner in winter—it can be drying.

If your skin is oily, you may want to switch to a light toner with a low concentration of salicylic or glycolic acid—.5 or 1 percent. In the morning, use a moisturizer—lotion or cream, not gel—with SPF 30. Look for one containing hyaluronic acid, which is excellent because it binds 10 times its weight in water, so it keeps the skin well hydrated. Petrolatum is also good.

If you're really dry, you can use moisturizers containing shea butter and oils...but never mineral oil on your face, because it blocks the pores. Apply a moisturizer again at night after cleansing, even if you've got oily skin. The acne-prone can skip the evening moisturizer in warm months. For those whose winter dryness is extreme, there's Mimyx, a safe and effective new prescription moisturizer that re-creates a natural barrier. It's worth a visit to the dermatologist, says Jaliman.

Bottom line: Change your routine in the fall, before the weather turns really cold, because it's much easier to prevent dryness and cracking than it is to treat it.