Moisturizers help prevent dryness, bruising, and tearing but have no effect on wrinkles by themselves. They should be applied while the skin is still damp. These products retain skin moisture in various ways:
Occlusives, such as petroleum jelly, prevent water from evaporating.
Humectants, including glycerin, act by pulling water up to the surface of the skin from deep tissues. People with oily skin generally should use the humectant type.
More powerful compounds, such as one called monolaurin (Glylorin), contain mixtures of fatty molecules called lipids, which may help restore the skin’s natural barriers against moisture loss and damage.
Most moisturizers contain combinations of these and usually have other ingredients, such as AHA, sunscreens, collagen, and keratin. (Collagen and keratin leave a protein film and temporarily stretch the skin.) They range widely in price, and a major consumer organization found little difference in general between the more and less expensive products.