COSMETICS VERSUS TOPICAL THERAPEUTIC AGENTS 439 7. Sun Screens The agents currently used as sun screens in cosmetics and pharmaceutical preparations are similar. They include the esters of p-aminobenzoic, anthranilic, salicylic and cinnamic acids which absorb ultraviolet radiation, primarily of wavelengths between 290 and 320 mu. Recently, the benzo- phenones (14), which absorb the longer wavelengths, and the acrylonitriles (15) have been recommended for use in pharmaceutical preparations. For cosmetic purposes, it might seem ideal to have a sun screen which would completely prevent sunburn and permit tanning which persists. There is doubt, however, whether such tanning can take place without at least some degree of previous burning. This type of tanning is dependent upon the formation of new melanin which in turn probably occurs only after cells have been injured in some way. Mild erythema (sunburn) may therefore be a prerequisite to a persistant tan. More recent work (16) has shown that the spectral range which can cause the formation of new melanin extends considerably beyond 320 mu, possibly to 650 mu. Even at these longer wavelengths, erythema often precedes the formation of new melanin in Caucasians, but at times pig- mentation appears to develop without clinical evidence of erythema. Photosensitivity and phototoxic reactions may follow exposure to the longer ultraviolet wavelengths (greater than 320 mu) and visible light. Since most of the sun screens used in cosmetics effectively absorb only radiation up to 320 mu, they are not satisfactory for use by a patient who has a photosensitivity. SUMMARY AND CONCLUSIONS There is an ever increasing similarity between the agents used in some cosmetics and some topical therapeutic preparations. Although the in- tended function of many cosmetics is the maintenance and/or improvement of the characteristics of relatively normal skin, while the intended function of topical therapeutic agents is usually the "cure" of abnormal skin, the general composition and mechanism of action of several categories of prod- ucts overlap. Emollients are common to both cosmetics and therapeutic preparations. Their mechanism of action has received considerable attention in recent years and is now fairly well understood. Some misunderstandings which have arisen have been reviewed. For cosmetic purposes, keratolytic agents are often used to soften hair the topical therapeutic agents of the dermatologists, on the other hand, are used to soften keratinized epithelium. Their compositions necessarily vary, as do their mechanisms of action. Although cosmetic cleansers are often similar to the cleansers recom- mended by dermatologists, both dermatologists and cosmetic chemists at

440 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS times suggest the use of "nonsoap" cleansers, some to be used with water and some without. The judicious use of soap and water for personal hygiene is seldom harmful to normal or to many abnormal skins. Topical antimicrobial agents effectively reduce the bacterial population of normal skin. For this, they are successfully used prophylactically by surgeons and dermatologists. Cosmetic manufacturers recommend them for control of body odor. Some dermatologists feel that known infections of the skin should be treated systemically rather than by topical antimicro- bial agents. There is as yet inadequate evidence to prove that micro6rganisms are important etiologic agents for cutaneous disturbances in the seborrheic areas of the skin (ache and dandruff). Some antiseborrheic agents may have antimicrobial properties, but it is not yet established that their mechanisms of action are dependent upon these properties. The exact mechanism of action of such agents as sulfur, selenium sulfide and zinc pyridine thione is not known. If aluminum salts successfully reduce the amount of sweat delivered to the cutaneous surface, the mechanism whereby they do this is not clearly understood. The dermatologist finds it difficult to control excessive sweating of the palms and soles by any topical therapeutic agents. For a very few people who have specific photosensitivities, it is important to protect the skin against a wide spectrum of the sun's radiant energy. This can be accomplished with partial success by some sun screens. The objective of the cosmetic sun screen is to protect the skin against too much exposure to the erythema-producing spectrum and permit the pigment- producing spectrum to reach the skin. This may be possible with the careful choice of the sun screening chemical and with avoidance of excessive exposure. It is thus apparent that there is sufficient overlapping of the interests of cosmetic chemists and dermatologists to render cooperative effort profitable to both groups. (Received June 10, 1963) REFERENCES (1) I. H. Blank, J. Invest. DermatoL, 18, 433 (1952). (2) I. H. Blank, Proc. Sci. Sect. Toilet Goods `4ssoc., No. 23, 19 (1955). (3) C. Fox, J. A. Tasoff, M. M. Rieger, and D. E. Deem, J. Soc. Cosmetic Chemists, 13, 263 (1962). (4) E.A. Taylor, dr. Invest. DermatoL, 37, 69 (1961). (5) C. N. Frazier and I. H. Blank, .4 Formulary for External Therapy of the Skin, Charles C Thomas, Publisher, Springfield, 111., 1954, pp. 92-94. (6) D. R. Goddard and L. Michaelis, J. Biol. Chem., 106, 605 (1934). (7) R. R. Suskind, dr..4m. Med..4ssoc., 163, 943 (1957). (8) R. B. Stoughton, L. W. Potts, W. Clendinning, S. Fisher, and M. Kress, Ibid., 173, 1196 (1960). (9) I. H. Blank and E. Gould, dr. Invest. DermatoL, 37, 475 (1961).