The benefit of face creams may be mostly in the mind. research has ... ence reported in skin cream advertisements. Dry skin ... oil in aqueous cream. The oil ...
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How credible is the science behind cosmetic skin creams? In order to answer this question it is important to separate the work done by cosmetic chemists in basic science, product development, and safety testing from the spin put on that work by salespeople, fashion magazine "editorials," and advertising companies promoting the creams, all of which mainly measure success by product sales. Cosmetic chemists' research is aimed at providing their employers with a competitive edge. Because most of their results are financially sensitive, they are never published. The work that is published often appears in conventional medical journals and is subjected to the same rigorous review process as other articles. In addition, groups such as the International Federation of Societies of Cosmetic Chemists regularly have congresses where scientific papers are presented. The presentations abstracted in the proceedings from the most recent congress, held in Sydney in 1996, are of varying quality; some are at the cutting edge of science whereas others are more dubious.1
Cosmetics are not pharmaceutical agents It is important to remember that cosmetics, by definition, do not alter the structure or function of the skin, or they would be classed as pharmaceutical agents. There are 2 broad groups of cosmetics: makeup and skin care products. The use of well-applied makeup to add color, accentuate the lips and eyes, conceal blemishes, or relieve dryness or oiliness may enhance a person's physical appearance and sense of well-being.2
Cosmetics are luxury items, designed to make the user feel better, irrespective of whether they have any lasting impact on the skin. On the other hand, skin care products have very little substantive science to commend them. Although extensive comparative
The benefit of face creams may be mostly in the mind.
research has been done using endpoints such as skin barrier function and epidermal cell turnover to produce products that perform
these functions well, the basic assumption that such products are required for skin health and maintenance is questionable. A basic understanding of skin physiology, skin aging, skin typing, pores, skin allergy, liposomes, collagen and elastin, hormones, and vitamins is required to validate the science reported in skin cream advertisements. Dry skin looks rough; moist skin looks smooth. How rough (dry) or smooth (moist) the skin appears depends on the hydration of the stratum corneum and its thickness. In the ichthyoses (genetic conditions that produce the appearance of dry skin), the skin's moisture content is normal. Thickening of the stratum corneum produces the appearance of dryness.3 These conditions respond only partially or not at all to moisturizers. Most people do not need moisturizers. Skin moisturizers act in 2 ways: as an emollient, by providing water to the surface of the skin, and by preventing transepidermal water loss, about 500 ml per day in temperate climates. The second action is more prolonged. The most effective moisturizers are agents such as white soft paraffin that provide
a waterproof seal on the skin, allowing it to be hydrated from within. Because white soft paraffin is greasy and difficult to rub into the skin, it is formulated into combinations of water and oil that are more user-friendly, such as 10% glycerine in sorbolene or 5% olive oil in aqueous cream. The oil component contributes most of the moisturizing effect; the water component makes it easier to apply to the skin. More expensive products do not moisturize the skin any more effectively but may have a nicer texture, rub into the skin more easily, and have a superior fragrance. The effectiveness of skin foods that nourish the skin, vitamins (in particular vitamin E), or hormonal extracts that replenish the skin is not supported by convincing science, and so these products are not recommended. Liposomes are a delivery system that encapsulates a cosmetic ingredient into microscopically small droplets, enabling better penetration ofthe ingredient into the epidermis. Currently this process has its limitations, but better systems may evolve in the future. Aging of the skin should be considered in terms ofchronological aging and solar aging.4 Most of the changes we associate with skin aging are in fact a result of solar damage, Volume 171 July 1999 wjm 35
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Best Practice
which produces wrinkling, loss of elasticity, variable pigmentation, and broken capillaries. Only creams that contain a sunscreen can be called "anti-aging." Nothing, except possibly creams containing retinoic acid, has been shown to reverse or prevent chronological aging. In the 1980s, a great deal of research was done to establish retinoic acid as an antiaging cream. Creams containing collagen and elastin are occasionally promoted for their anti-aging or anti-wrinkle effects, but they have none. These are large molecules, incapable of penetrating the epidermal skin barrier to gain access to the dermis, where the aging process predominantly occurs. Skin typing is a creation ofwomen's magazines and people who sell cosmetics. There is no normal skin type. The oiliness or dryness of one's skin changes from day to day, even from hour to hour during the day.
The function of pores Pores correspond to the ostium ofhair follicles and eccrine sweat glands. They are static, and no cosmetic is capable of altering their size or shape. The need for toners or astringents seems to be generated by the desire to remove other skin care products, leading to the creation of a skin care routine.
There is a strict code of ethics governing the advertising of pharmaceutical and cosmetic products, but the cosmetic industry frequently bypasses this code by commissioning editorial comments in fashion magazines from poorly informed journalists. These comments are read uncritically by beauticians and sales representatives, who further perpetuate the inaccuracies. Many products carry an endorsement by dermatologists or an institute oflearning. My only personal experience with product testing, when I was a student at Oxford, involved the evaluation ofa device to remove hair. The product claimed that its electronic tweezers could send an electric current down the hair follicle to the bulb and produce permanent hair destruction. We showed that the product did not do this and was no more effective than simply plucking hair, and we made this clear to the manufacturer. Nevertheless, I subsequently spotted an advertisement for the product, promoting it as being tested by dermatologists at Oxford University. Not surprisingly, the test results were not mentioned. The science behind cosmetics is strong. There are abundant data on toxicology. Extensive work is done to develop a product
that is better than its competitor in terms of touch, feel, and smell. After all, if the product is no good, then no amount of advertising will generate repeat sales. What is more questionable are the assumptions made by the cosmetic industry and the consumer: if you use moisturizers then you may need a skln care routine, incorporating toners and astringents to remove them. In the end, it is all consumer-driven. Cosmetics are luxury items, designed to make the user feel better, irrespective ofwhether they have any lasting impact on the skin. Rodney Sinclair Departmnent of Dermatology St. Vmcent's Hospital University of Meurne 206 Albert Street Melbourne 3002, Australia References
1 Proceedings of the 19th International Federation of Societies of Cosmetic Chemists International Congress 1996; Sydney, Australia. 2 Berger P Skin secrets. Sydney: Allen and Unwin; 1991. 3 Champion RH, Burton JL, Ebling FJG. Textbook of dermatology. 5th ed. Oxford: Blackwell Science; 1992. 4 Marks R. Skin disease in old age. London: Martin Dunitz; 1987.
This paper was originally published in the Student BMJ 1998;6:286-287.
PRACTICE POINT
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