Unexplained dry skin can be frustrating and painful. Cracks and flakes do not lend a professional appearance to your hands, face, or other body parts, and you could have limited mobility in the affected area (e.g., the knuckles of your hands) because moving stretches and hurts the dry skin too much. But there could be some very easy-to-fix problems behind the dry skin.
It's easy to end up deficient in a vitamin or two even if you try to eat a healthy diet. Calorie restriction, fad diets, eating too much fast food, and so on can all make your vitamin levels go out of whack. Vitamin B2 (aka riboflavin) and vitamin E are both relatively easy to get in your diet, but if you just don't eat the foods that contain them, you can easily find yourself deficient. Lacking either of these vitamins can result in dry skin. Taking a supplement or increasing the foods in your diet that have these vitamins should help.
Sometimes, it's not the diet that's the problem but your activities. If you don't go outside much, or if you wear sunscreen all the time when you're outside, you can easily develop a vitamin D deficiency. Vitamin D's connection to skin health is still under investigation, but getting more sunlight or taking a supplement may help soothe dry skin. There was even a study that found applying a topical cream with vitamin D helped reduce dry skin.
Too Much Hot Water, Cold Air, or Other Temperature Extreme
Not everyone suffers dry skin as a result of excessively low humidity in winter, hot and dry summers, or another combination of temperature and climate factors. But if you were one of these lucky people and you've just moved to a new part of the country -- and the dry skin seemed to happen at just about the same time -- you're looking at climate or weather as the cause. Moisturizers, humidifiers, and other protection like wearing gloves on very dry days can help combat these causes.
Not Enough Fat
This one has what may be one of the more delightful cures: You might not be getting enough fat in your diet, so go have something fatty. To a point, of course. Dietary fat does play a role in keeping skin looking good, and eating a diet that is too low in fat (SELF magazine notes that 25 to 35 percent of your calories as fat is generally good) can dry you out rather drastically. You do want the fat to be high quality and preferably monounsaturated -- especially those omega-3 fats, per that same SELF article. So look at olive oil, nuts, wild fatty seafood, and more as potential additions to your diet. Try to keep the pizza and ice cream under control, though.
If you're still having trouble with dry skin, talk to a dermatologist who can investigate the problem further. Give each of these remedies a few weeks to work, but don't wait much longer than that to see a professional if the remedies aren't working.