"Cold weather and central heating result in less humidity in the environment and more evaporation of water, otherwise known as increased transepidermal water loss from the skin surface, leading to dryness," Dr. Mahto explains, which is why it pays to invest in products that keep moisture under lock and key when the temperature drops. But whatever you do, don't introduce them all at the same time. "Making a large number of changes to your skin-care routine at once has the potential to disrupt your skin barrier, which can result in further dryness, irritation, sensitivity, and even eczema or dermatitis," she says. "Start with one product and gradually build it into your routine as tolerated before adding in extra steps or layers. This will minimize irritation and dryness."