February 7, 2009
How moisturizers help the skin appearance?
Moisturizers act primarily to restore skin hydration. Hydration appears to be essential to healthy appearance. Poor hydration results in dryness. And dryness results in skin flakiness, dryness and roughness. Only a few skin moisturizers have been scientifically studied.
Petrolatum the most commonly used occlusive substance, is able to decrease water loss by about 50%. However, petrolatum does not produce any increase in hydration. Cells in the skin called corneocytes prevent water loss and help the to act as a barrier to the outside world. These cells or corneocytes also contain natural moisturizing factors that help hold water molecules.
Moisturizers are made with:
- Occlusives
- Humectants
- Emollients.
Occlusives prevent water loss and are made of oils or fats such as petroleum, lanolin, mineral oil, vegetable oil, or waxes.
Humectants are low-molecular-weight substances that attract water. Natural moisturizing factors are naturally occurring humectants. Common humectants used in moisturizers are glycerin, propylene glycol, and urea.
However, there have been few clinical studies demonstrating the hydrating effects of humectants. Gloor and Gehring demonstrated that a topical application of 85% glycerol emulsion for 3 weeks in volunteers with normal skin resulted in significant reduction in total water loss from skin.
Emollients have no hydrating properties, but they are often used in moisturizers to act as a filler between dead corneocytes thus making the skin smoother.
Scientific studies of moisturizers have been inconsistent. A study that used a moisturizer containing 20% glycerine showed no improvement hydration.
A vitamin B analog called nicotinamide has been shown to improve hydration. Nicotamide appears to work by stimulating corneycyte cells to make ceramid, glucosylceramide and sphyingomyelin. These are fats important to maintaining hydration in normal skin.
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