Dry skin isn’t dangerous for itself, but severe cases can cause cracks and fissures, which invite infection and inflammation. Dry skin can be painful, tender, and itchy (although not all itchy skin is dry). There’s also the red, rough, scary look that many moisturizer ads regret.
There are plenty of creams and lotions for dry skin, but this is one issue that hasn’t gotten much attention. They’re marketed as moisturizers, so that’s a marketing word rather than a medical or scientific term. Routine skincare, in fact, is a field where little science can be discovered. Ingredient experiments that are well-controlled are few and far from being scientific proof. To remain within FDA guidelines, companies keep information about ingredients confidential and reduce claims about what the products can do.
Despite the long lists of obscure ingredients and pseudoscientific nonsense, all moisturizers help with dry skin for the same reason: they provide a small amount of water to the skin and contain a greasy substance to keep it in. In fact, if greasiness wasn’t an issue, we would all go back to using the same dry-skin solution that our grandparents did: 100 percent white petrolatum, also known as Vaseline. The ongoing search for a blend of ingredients that holds in water like petrolatum but feels better on the skin is one reason for the proliferation of moisturizers.
Water is the key
Because most moisturizers are oil-in-water emulsions, they are creams and lotions by definition. When you look at the ingredient list, you’ll notice that water is often listed first. When you apply the moisturizer, some of the water evaporates, but some soak in. While the stratum corneum absorbs water well, it does not bind it well, necessitating the use of an oily substance to keep it in. Applying an oily substance to the skin without also rehydrating it with water — whether from the moisturizer or another external source such as a bath — is ineffective: you’ll end up with greasy skin that is still dry and cracked. In fact, the only way to soften skin is to soak it in water for a long time.