High-concentration glycerin serves as humectant to attract water to skin

March 1, 2011

High-concentration glycerin is being added to many moisturizers to function as a humectant, aiding in attracting water to the xerotic skin surface. While glycerin is a highly effective moisturizing ingredient in low-humidity climates, it can leave skin with a sticky feel in humid environments. This is because glycerin can also attract water from the air.

Key Points

Q. How do moisturizers change skin aquaporins?

A. Aquaporins are water channels present in all cells of the body, including the skin. They have been highly conserved through evolutionary development and are found not only in humans but in all living organisms, including plants, fish, reptiles and amphibians. Proper aquaporin function is essential to maintaining water balance by preventing dehydration and overhydration of the cell, both of which would result in death.

Glycerin is the oldest new ingredient introduced into many therapeutic moisturizers. In many cases, it is the basis for the "therapeutic" claim. It is interesting to note that glycerin is the sole ingredient in Corn Husker's Lotion, one of the first hand moisturizers introduced into the U.S. marketplace. Expect to hear much more from glycerin, as aquaporins also appear to modulate aspects of cellular differentiation. It is an ingredient with great potential as aquaporins in the skin are better understood.

Q. Does cleanser foam equate with skin hygiene?

A. It is a common misconception that soap must foam in order to clean. This is not true. Consumers believe that the more a soap foams, the better it must be removing dirt.

Actually, the opposite is true. Soap foams as the detergent is mixed with water, but as the detergent emulsifies the sebum and environmental dirt, the foam disappears. The oil actually prevents maintenance of the soap bubbles. The cleaner the skin and hair, the more foam produced by the cleanser.

Manufacturers of bar cleansers, liquid cleansers and shampoos know that consumers like abundant foam, thus they add foam boosters to formulations for aesthetic purposes and not functional needs. Thus, cleanser foam does not equate with skin hygiene.

Q. What is a hair serum and does it feed the hair?

A. A variety of new haircare products have been introduced to moisturize the hair. Serums were first introduced into the skincare market as cosmeceuticals intended to deliver an active agent to the skin surface followed by application of a moisturizer. Skin serums contained ingredients such as vitamin C, ferulic acid and peptides. The serum was a thin liquid to offer a more concentrated "treatment" ingredient without other associated skin benefits.

This concept has now been adapted to haircare products. Primarily, the new hair serums contain dimethicone to provide a shiny film over the hair shaft, decrease static electricity by neutralizing any electrical charge on the hair and reduce the frizzy appearance of the hair. Dimethicone can achieve these goals without making the hair greasy and lifeless. Hair serums are concentrated moisturizers that are quite efficacious in damaged, chemically treated hair.

Zoe Diana Draelos, M.D., is a Dermatology Times editorial adviser and consulting professor of dermatology, Duke University School of Medicine, Durham, N.C. Questions may be submitted via e-mail to zdraelos@northstate.net
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