J. Soc. Cosmetic Chemists, 17, 581-594 (1966) New Evaluation for Sunscreens Techniques KARSON .J. MASTER, Ph.D.,* ROBERT M. SAYRE, M.A.,t and MARK ALLEN EVERETT, M.D.• Presented December 1, 1965, New York City Synopsis--New techniques contributing to the laboratory evaluation of chemical, physical, and chemical/physical combination sunscreen products are presented. These enable deter- ruination of direct and total transmission, absorption, and reflection of ultraviolet and visible light through transparent or translucent thin films similar to those applied on the skin. The classical solution-dilution method usiug a Beckman Model DB Spectrophotometer and a new thin film technique using a xenon arc Monochromator and Cary Model 14 Spectro- photometer with integrating spheres were investigated. ]n vitro and in vivo measurements were made. INTRODUCTION Sunburn, photosensitivity reactions, aging, and carcinogenesis are some of the undesirable cutaneous responses to sunlight most com- monly encountered by the dermatologist. Blum (1), Bachem (2), Everett (3), and Knox (4) have reviewed the physiological and the pathological cutaneous reactions to sunlight resulting from its broad action spectrum from the ultraviolet through the visible (290 to 740 mu). In recent years, considerable activity has been evidenced in the cosmetic and pharmaceutical industry in developing products capable of efficiently screening out the harmful portion of the spectrum of light. This has resulted in the investigation of more effective and broad spec- * Westwood Pharmaceuticals, Division of Foster-Milburn Co., Buffalo, N.Y. 14213. } Department of Dermatology, University of Oklahoma Medical Center, Oklahoma City, Okla. 73104.

582 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS trum physical and chemical sunscreens and their combinations in cos- metically elegant and functionally effective bases. Laboratory evalua- tion of such products, utilizing the classical methods, has failed to keep pace with the progress achieved in other areas in the field. Presented below 'are studies leading to a more adequate and meaningful evaluation of sunscreens and techniques devised to obtain representative, practical, and meaningful information regarding their physiological effectiveness. CHEMICAL AND PHYSICAL SUNSCREENS Chemical sunscreens are agents that protect the skin by absorbing and dissipating the energy of the damaging ultraviolet sunburn rays. Organic compounds which have absorbed radiation are either raised to a higher energy level or dissociated. The excited molecules may dissipate their absorbed energy by collision, fluorescence, or a reaction with other molecules at collision (5). p-Aminobenzoic acid and its derivatives have been the most widely employed suncreening agents. Physical sunscreens (sunshades) are opaque, usually insoluble chemicals that produce their effect by reflecting and scattering light. Examples are titanium dioxide, talc, kaolin, zinc oxide, and bentonitc. Occasionally these agents are used in combination with chemical sun- screens to complement the protection afforded by the latter. Even a cream vehicle will sometimes provide protection. In this study the following experimental sunscreen products were studied: A. Chemical Sunscreen: 7.0% p-aminobenzoic acid in a clear viscous solution B. Physical Sunscreens: (1) Opaque cream base (2) 10% talc in opaque cream base C. Chemical,/Physical Sunscreen: 5% amyl p-dimethylaminobenzoate and 10% talc in opaque cream base SOLUTION-DILUTION METHOD The current laboratory method of evaluating sunscreens involves quantitatively dissolving the finished product containing the sunscreen in an ultraviolet-transparent solvent such as isopropanol, filtering the solution, preparing dilutions, and measuring transmission (6). Figure 1 shows the transmission curves determined for the experi-