Last Updated: September 5, 2006
AUTHOR INFORMATION Section 1 of 10
Author Information Introduction Moisturizers Retinoids Hydroxy Acids Antioxidants Depigmenting Agents Other Cosmeceuticals Conclusion Bibliography
Author: Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Medicine, Professor of Pediatrics, Professor of Pathology, Professor of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School
Coauthor(s): Santiago A Centurion, MD, Staff Physician, Department of Dermatology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey; Cristina S Solis, RN, BSN, Consulting Staff, Department of Dermatology, UMDNJ-New Jersey Medical School
Robert A Schwartz, MD, MPH, is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, and Sigma Xi
Editor(s): Zoe Diana Draelos, MD, PA, Clinical Associate Professor, Department of Dermatology, Wake Forest University; Clinical Associate Professor, Department of Dermatology, Bowman Gray School of Medicine; David F Butler, MD, Professor, Texas A&M University College of Medicine; Director, Division of Dermatology, Scott and White Clinic; Christen M Mowad, MD, Assistant Professor, Department of Dermatology, Geisinger Medical Center; Catherine Quirk, MD, Clinical Assistant Professor, Department of Dermatology, Brown University; and William D James, MD, Paul R Gross Professor of Dermatology, University of Pennsylvania School of Medicine; Vice-Chair, Program Director, Department of Dermatology, University of Pennsylvania Health System
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INTRODUCTION Section 2 of 10
Author Information Introduction Moisturizers Retinoids Hydroxy Acids Antioxidants Depigmenting Agents Other Cosmeceuticals Conclusion Bibliography
Cosmeceuticals represent a marriage between cosmetics and pharmaceuticals. Like cosmetics, cosmeceuticals are topically applied, but they contain ingredients that influence the biological function of the skin. Cosmeceuticals improve appearance, but they do so by delivering nutrients necessary for healthy skin. Cosmeceuticals are the fastest-growing segment of the natural personal care industry. Consumers are always interested in maintaining a youthful appearance, and as the global population's median age increases, this market is increasingly expanding.
Cosmeceuticals are not subject to review by the Food and Drug Administration (FDA), and the term cosmeceutical is not recognized by the Federal Food, Drug, and Cosmetic Act. Although cosmetics and cosmeceuticals are tested for safety, testing to determine whether beneficial ingredients actually live up to a manufacturer's claims is not mandatory. In general, vitamins, herbs, various oils, and botanical extracts may be used in cosmeceuticals, but the manufacturer may not claim that these products penetrate beyond the skin's surface layers or that they have druglike or therapeutic effects. For cosmetic labels, no division between active ingredients and other ingredients is required; they are all listed together.
The most important botanicals pertaining to dermatologic uses, such as cosmeceuticals, include teas, soy, pomegranate, date, grape seed, pycnogenol, horse chestnut, German chamomile, curcumin, comfrey, allantoin, and aloe; only green and black tea, soy, pomegranate, and date have been studied to the extent that clinical trials for the treatment of parameters of extrinsic aging have been published (Thornfeldt, 2005). Few botanical-based cosmeceuticals have uses that are supported by evidence-based science.
Chemoprevention by oral or topical use of dietary or pharmacologic agents to inhibit or reverse the development of cancer is a possibility (Wright, 2006). Potential cosmeceutical agents in this category include green tea, grape seed extract, vitamin E, and beta-carotene.
MOISTURIZERS Section 3 of 10
Author Information Introduction Moisturizers Retinoids Hydroxy Acids Antioxidants Depigmenting Agents Other Cosmeceuticals Conclusion Bibliography
The cutaneous permeability barrier is localized in the stratum corneum interstices, and it is mediated by the lamellar bilayers enriched in cholesterol, free fatty acids, and ceramides. Formulations containing skin-identical lipids have been suggested to facilitate a cascade of physiologic events in keratinocytes, normalizing damaged skin. When applied to the skin for an extended period, water can cause the excretion of cytokines. These proinflammatory molecules induce edema, vasodilation, and frank inflammation; therefore, water alone may alter both the structure and the function of the skin under some conditions. By the same token, moisturizers that make the stratum corneum softer and more pliant by increasing its hydration could be considered cosmeceuticals.
RETINOIDS Section 4 of 10
Author Information Introduction Moisturizers Retinoids Hydroxy Acids Antioxidants Depigmenting Agents Other Cosmeceuticals Conclusion Bibliography
Retinoids are possibly the most prevalent cosmeceuticals in the market. Retinoids are vitamin A derivatives present in all living organisms either as preformed vitamin A or as carotenoids. Vitamin A (retinol) is the prototype of all other retinoids and is necessary for proper growth, bone development, and integrity of mucosal and epithelial surfaces. In vitamin A deficiency, the eyes and the skin are severely affected. The conjunctiva and the cornea develop metaplasia and keratinization, leading to night blindness. The skin develops follicular hyperkeratosis or phrynoderma. The hyperkeratotic follicular papules are usually clustered around bony prominences, such as the elbows and the knees, but in severe deficiency, the papules can be found throughout the entire skin surface.
Early civilizations recognized the benefits of vitamin A in treating and healing night blindness with diets rich in liver. In the 1930s, the clinical manifestations of vitamin A deficiency were recognized, and the idea to use vitamin A in the treatment of skin diseases was initiated. The advent of synthetic analogs of vitamin A in the 1970s brought new interest into their biological activity, especially on the skin. Since then, vitamin A and its derivatives have been useful in the treatment of many skin disorders, including ichthyosis, acne, and psoriasis. A great amount of research has concentrated on its use as an antiaging compound as well as its use for other cutaneous disorders; therefore, today, vitamin A is recognized as comprising a magnitude of biological effects far beyond those on the cornea.
Vitamin A and its derivatives have 2 main functions: they act as antioxidants, and they activate specific genes and proteins. As antioxidants, they protect cells from oxidative damage by 3 different mechanisms: (1) scavenging peroxyl radicals, (2) quenching singlet oxygen, and (3) triplet-state sensitizers. Vitamin A also exerts a hormonelike effect on the skin, activating specific genes through nuclear receptors. The receptors bind to target sequences called hormone response elements on DNA and activate gene transcription. Retinoic acid receptors (RARs) bind all-trans retinoic acid, and retinoic X receptors (RXRs) bind 9-cis retinoic acid. Vitamin A and its derivatives inhibit lipid peroxidation; increase levels of alpha-tocopherol (vitamin E); and activate growth factors, oncogenes, keratins, and transglutaminases.
Histologically, vitamin A and its derivatives induce epidermal thickening, increase mitoses, differentiate keratinocytes, and reduce the number of sebocytes. The dermis shows increased amounts of glycosaminoglycans (GAGs) and anchoring fibrils. Structural changes underlying the cosmetic benefits include correction of epidermal atrophy, deposition of new collagen, generation of new vessels, and enhancement of mitogenesis. This enhanced mitogenesis promotes the shedding of melanin-laden keratinocytes, resulting in bleaching and subsequent depigmentation. The ability of topical tretinoin to improve the appearance of aged and photo-damaged skin by reducing wrinkles, decreasing laxity, bleaching hyperpigmented spots, and bringing about a smoother surface have been well studied and documented. Further remedial qualities of retinoids remain to be elucidated.
Importantly, the effectiveness of the non–FDA-approved cosmetic retinoids has been studied. Clinical and histological evidence suggests structural changes induced by excessive sun exposure can be partially reversed by the use of topical retinoids, such as retinaldehyde. They have been used for the treatment of photoaged skin with demonstrated beneficial clinical and histological effects (Stratigos, 2005). Because clinical correlates of these in vitro findings are not entirely convincing, with most studies being poorly constructed, the utility of these preparations for their stated uses is regarded by many authorities as marginal at best.
