Protein glycation, substantivity play important roles in skincare

Key Points

Q What is protein glycation and how does it affect the skin?

Protein glycation is the binding of a sugar to a protein. The brown color of toasted bread is the binding of sugar with the protein in the bread flour to produce the aesthetically pleasing golden-brown color. The brown color caused by self-tanning creams is due to the binding of the sugar dihydroxyacetone to the protein of the stratum corneum. This glycation reaction produces melanoidins, which temporarily stain the stratum corneum brown. None of these reactions produce health issues.

The glycation of tissues is hastened in diabetes, making a research model for the effects of glycation in the body. Excess protein glycation in the body leads to decreased tissue functioning and premature aging. Individuals who exhibit lower internal protein glycation have less systemic disease and slower aging.

Q Why is "substantivity" important to skincare?

A Substantivity is a word used in the cosmetics industry to describe the ability of a skincare product to remain in place on the stratum corneum. This concept is very important in the efficacy of sunscreens and the performance of facial foundations.

The ability of a sunscreen to deliver long-lasting sun protection depends not only on the photostability of the filter, but also on the ability of the filter to remain in a thin, even film over the skin's surface. When the sunscreen is rubbed onto the skin, it is distributed in an even film, but the film will migrate with movement, sweating, water contact and rubbing. The ability of the film to stay where it was put is substantivity.

Products with a high substantivity will deliver the labeled SPF for a longer period. One of the most important reasons why sunscreens fail is reduced substantivity, and substantivity is not taken into account by traditional SPF testing. This is why some experts recommend taking the labeled SPF and cutting it in half for actual performance.

Substantivity is also important in the performance of facial foundations, which are designed to camouflage blemishes, add color and create the illusion of perfectly smooth skin. If a facial foundation remains in an even film on the skin surface, it will demonstrate excellent substantivity and appear attractive for longer. Facial foundations with poor substantivity will migrate into the dermatoglyphics of the face and "disappear." The foundation actually does not disappear, but the discontinuous film will not create the illusion of perfectly smooth skin, and the wearer will feel it necessary to reapply the cosmetic.

Q What is the ORAC score and how is it relevant to topical antioxidants?

A The ORAC score was originally developed to rate the oxidative damage in foods as it relates to nutrition. There was concern about the vitamin content of frozen and canned foods, so the ORAC scale was developed by the federal government.

The ORAC scale was never intended to be used for evaluation of the antioxidant potential of substances used on the skin surface. This is why the products that claim to have a higher ORAC score than vitamin E, such as idebenone, are not necessarily superior skin antioxidants. Vitamin E is the primary physiologic antioxidant in the skin, and higher ORAC score substances are not biologically relevant.

Zoe Diana Draelos, M.D., is aDermatology 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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