If you’ve ever pulled an all-nighter or gone without sleep for more than two days in a row, you know what happens. You start to feel groggy, and eventually have trouble concentrating. You might even hallucinate. Go without sleep for too long and, as studies using rats have shown, you can die. Clearly, our bodies need sleep. Learn more on this Moment of Science.
So what is actually happening when a moisturizer is rejuvenating your skin? First, moisturizers help your skin stay hydrated by either forming a barrier that prevents the water in your skin from evaporating, or by pulling water from the skin’s inner layers out to the skin’s surface.
Ironically, the general covering of our bodies in hair — what we call “fur” on other animals — is at the root of our problem with acne.