.7. Soc. Cosmetic Chemists, 15, 709-716 (1964) SOME COMMENTS AND SUGGESTIONS FOR THE MEASUREMENT OF THE PROTECTIVE EFFECT OF SUNSCREENS* By FARRINGTON DANIELS, JR., M.D., M.P.H.I Presented May 8, 1963, Semi-/lnnual Scientific Meeting of the Society of Cosmetic Chemists Held in yoint Sponsorship with the/lmerican Medical /lssociation Committee on Cosmetics ABSTRACT Testing of sunscreens is complicated, because of the complicated optics of the skin surface and the relationship between different wave- lengths of ultraviolet radiation and the erythema response. Studies are reported, indicating that small test areas may be as useful as large test areas where erythema is the end point. Quantitation of small test areas by means of photography through narrow band pass inter- ference filters with grey scale calibration is discussed. At first glance the problem of testing sunscreen preparations would appear to be extremely simple all one has to do is to give a sunscreen preparation to a group of people and have them try it out under actual field conditions. A more sophisticated test would be to apply various test preparations to different areas and to observe whether protection did or did not occur. The trouble with these simple forms of testing is that they provide only a limited amount of information, and also, that they tend to ignore many of the complicated aspects of wavelength distribution in sun- light and the responses of the skin to different wavelengths. •VHAT IS WRONG WITH INDIVIDUAL TESTING AND TESTIMONIAL DATA ? My own experience has been more in the testing of photosensitizing compounds than it has been in testing sunscreens. However, at the time some of the tests were conducted, the photosensitizers were being advo- * Supported by USPH Grants C-5052, C-6316 and CA-07071. t I)ermatology Div., Cornell University Medical College, New York, N.Y. 709

710 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS cated as sunburn protectives, and the testimonial data and the possible re- actions are relevant to the present problem. With the collaboration of several practicing dermatologists, Hopkins, Fitzpatrick, and I (1) studied the reactions of a group of patients to a placebo and to a probably inef- fective dose of 8-methoxypsoralen. In spite of the fact that we were deal- ing with an extremely potent photosensitizing agent, the statistics indi- cated that the results had been overwhelmed by a variety of enthusiastic placebo reactions. Individuals who had the greatest problem with sun- burning and poor tanning claimed the most beneficial results from the placebo. It is easy to understand these placebo reactions in terms of the social pressures of our day. Our modern culture has revived ancient sun- worship but unfortunately contains many individuals whose ancestors for at least 10,000 years and perhaps 100,000 years have undergone selection for adaptation to a cloudy, foggy or glaciated environment (2). Thus, the girl with the peaches and cream complexion inherited from her beautiful grandmother is now expected to have a healthy "tanned" look and to be able to tolerate daylong ultraviolet exposure at seaside or poolside. Toler- ance to the environmental factor of ultraviolet radiation is much more of a social problem than adaptation to high altitude, cold or ability to hold one's breath under water without drowning. Another source of error in the evaluation of the alleged protective effect of ingested 8-methoxypsoralen was the variation between individuals in their interpretation of the definition of sunburn. Some subjects appeared to evaluate sunburn in terms of redness and some in terms of subjective sensations. Since the 8-methoxypsoralen produced a delayed, protracted erythema without much pain or tenderness, many of the subjects inter- preted the results as protection. Their conclusion tended to be, not that they had had a photosensitization reaction, but that they had a potentially severe sunburn from which they had been spared the subjective discomfort of their previously experienced sunburns. They thought of the enhanced erythema in such terms as "If I got this red on the pill, just think how bad I would have been without it !" QUALITATIVE EVALUATION OF SUNSCREEN AGENTS The usual manner of testing sunscreen preparations seems straightfor- ward enough. Different preparations are applied to different areas of the skin and the test and control areas exposed to sunlight or a suniamp. Ab- sence or reduction of erythema in test areas compared to control areas is presumptive evidence of protection. The most extensive studies of methods and problems in testing topical sunburn preventives have been reported by Blum (3, 4). His conclusions are expressed in mathematical terms which have discouraged me and, probably, many others from following directly in his footsteps. The prob-