The short answer
Winter dries skin from several directions at once: cold outdoor air, heated indoor air, hot water and frequent handwashing. Skin that was fine in October can look dull and feel tight by January. The habits that help most are cooler showers, patting dry, and moisturizing within a few minutes while skin is still damp.
Why it happens
Cold air holds much less moisture than warm air. When temperatures drop, the air outside gets dry, and your skin gives up water to it a little at a time. You step indoors, where heating makes the air dry again. Skin spends the whole day in air that pulls water from it, and there is no break.
Hot water adds to the problem. A long, hot shower on a cold morning feels wonderful, and it also strips away the natural oils that help skin hold on to water. The tight, rough feeling after you dry off is your skin telling you so. Wind, wool sleeves and frequent handwashing wear on it further. Hands usually show it first, since they are exposed to all of it.
Some areas have a harder time than others. Shins, forearms, hands and lips are common trouble spots. They are exposed, they get washed often, and in the case of shins they make little oil of their own. Older skin tends to dry more easily too, which is one reason so many questions about winter skin come from older adults.
Dry winter skin looks dull, rough or scaly. It can feel tight, itchy or scratchy under clothes. For many people it is more a matter of comfort and appearance than anything else, and a few changes to the daily routine make a visible difference.
What helps
Start with water temperature. Warm is better than hot, and shorter is better than longer. If a hot shower is a winter comfort you do not want to give up, keep the hottest water away from your hands and legs, and cut the time when you can.
Use a gentle cleanser only where you need it. Underarms and feet need washing more than shins do. Less soap on dry areas means less stripping.
Pat your skin with a towel when you get out, and stop while it is still slightly damp. Rubbing roughens the surface and takes away moisture you want to keep.
Moisturize within a few minutes of drying off. This habit matters more than the particular product. Skin that is still damp has some water at the surface, and a moisturizer on top holds it there. Waiting until you are fully dry and dressed leaves less to hold in.
Thicker products work better in winter than thin ones. Lotions have a lot of water, and they tend to leave the skin quickly in dry air. Butters and balms have no water, and they stay on the skin longer. Pure Shea is one example. It is a single ingredient, cold pressed unrefined East African shea butter, and it is solid in the jar. It melts at body warmth, so a small piece rubbed between your palms turns soft and spreadable. It goes on hands, elbows, lips and cuticles.
For rough, tight spots that need something richer, a balm such as Golden stays in place well. It is shea based, with oat kernel flour and rice bran extract, and it is made for face, body and scalp.
Add moisture to the air where you sleep. A humidifier in the bedroom helps when the heat runs all night. Clean it on the schedule the maker gives, because a dirty one does more harm than good. Keep the thermostat modest if you can, since very warm rooms are very dry rooms.
Protect your hands from the weather and from water. Wear gloves outside, and wear them again for dishes and cleaning, since hot water and strong soap strip skin quickly. At night, put a thick layer of moisturizer on your hands and slip on a pair of cotton gloves. By morning, hands tend to look and feel softer.
Feet respond to the same trick. A thick layer at bedtime and clean cotton socks keep it from rubbing off on the sheets. Lips like a little butter or balm too, especially before going out in the wind.
Choose soft fabrics against dry areas. Wool is warm, but it can feel scratchy on tight, dry skin. A thin cotton layer underneath makes a noticeable difference.
When to ask for help
Ordinary winter dryness is uncomfortable but usually manageable at home. Ask your doctor if your skin turns red and painful, if it bleeds or weeps, or if itching keeps you up at night. Ask too if rough patches keep returning no matter how steadily you care for them, or if one patch looks different from the rest. Those signs point to something a moisturizer is not meant to handle.
Your pharmacist can also help. Some medicines dry the skin as a side effect, and it is worth asking whether anything you take could be playing a part. Bring a list the next time you stop in.
The AHOTO note
Pure Shea and Golden both contain no water, which is why they sit on the skin longer than a lotion. Pure Shea is one ingredient with no added scent. Golden contains oats and soy and a light essential oil blend, and a patch test on your inner forearm is recommended before first use.