NEW EVALUATION TECHNIQUES FOR SUNSCREENS 593 reflection of the skin in vivo with or without the protection of a sunscreen. This appears to be true in the visible as well as in the ultraviolet range. The slight differences between the reflectance spectra could be as easily attributed to differences in pressure or positioning of the subjeet's hand over the opening to the integrating sphere. The fact that in one experiment the skin with the sunscreen actually reflected less light than the skin without sunscreen, while in the other two experiments the re- verse of this occurred, would tend to support the contention that posi- tioning, pressure, and trauma from applying the sunscreen may be more influential in changing the reflection spectra than the actual physical additive. Further studies are in progress to obtain information as to how changes in the circulation and the trauma of application of the sun- screen affect the reflection of the human skin and how to modify the equipment to eliminate these drawbacks. •UMMARY Development of sun-protective preparations must continue to pro- vide products giving a broad range of protection against the undesirable cutaneous responses to sunlight, such as sunburn, photosensitivity reac- tions, accelerated aging, and carcinogenesis. Most of the products available provide protection against sunburn and promote increased pigmentation. One of the drawbacks is a lack of a suitable laboratory method that will yield realistic information about the protective ability of the sunscreen product without the need for prolonged and strong ex- posure tests in humans to sunlight and other light sources with similar spectra. Use of the thin-film technique presented in this paper with a xenon are monochromator has afforded such information. Modifying this method by using integrating spheres with a Cary speetrophotometer Model 14, in place of the monochromator, has made it possible to meas- ure the total transmission or forward scattering and reflection or back scattering in addition to the direct transmission usually measured. The thin film technique makes it possible to determine rapidly these measurements on the sunscreen films simulating those applied on the skin without altering in any way the sunscreen product, as is commonly done with the dassie solution-dilution method. The new method has, in addition, made it possible to evaluate not only the chemical sunscreens but also the physical sunscreens and chemical/physical sunscreen com- binations. This has not been possible with previously published standard laboratory methods. The versatility of the thin film technique

594 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS makes it possible to measure the protective ability of sunscreen products on excised human epidermis as well as conduct similar measurements on human skin in situ. (Received February 16, 1966) REFERENCES (1) Blum, H. F., Physiol. Rev., 25,483 (1945). (2) Bachem, A., Am. J. Phys. Med., 35, 177 (1956). (3) Everett, M. A., Medical Times, 88, 1389 (1960). (4) Knox, J. M., Mod. Med. Can., 17, 85 (1962). (5) Blum, H. F., Photodynamic Action and Diseases Caused by Light, Reinhold Publishing Corp., New York, 1941. (6) Kreps, S. I., Proc. Sci. Sect. Toilet Goods Assoc., 23, 13 (1955). (7) Sayre, R. M., Straka, E. R., Anglin, J. H., Jr., and Everett, M. A., J. Invest. Dermatol., 45, 190 (1965). (8) Yeargers, E., and Augenstein, L., Biophys. J., 5,687 (1965). (9) Spruit, D., J. Invest. Dermatol., 42,285 (1964). (10) Everett, M. A., Yeargers, E., Sayre, R. M., and Olson, R. L., submitted for publication.