FLUIDITY IN SEMISOLIDS VIA ESR 9 towards diffusivity studies, with the ultimate aim of optimizing vehicle selection in controlling drug release processes. REFERENCES (1) B. W. Barry, "Rheology of Pharmaceutical and Cosmetic Semisolids," in Advances in Pharnazceutical Sciences, H. S. Bean, A. H. Beckett, and J. E. Carless, Eds. (Academic Press, London, New York, 1974), Vol. 4, pp. 1-72. (2) J. D. Ferry in Rheology, Theory and Applications, F. R. Eirich, Ed. (Academic Press, New York, 1958), Vol II, pp. 433-473. (3) W. Kuhn, Relaxationszeitspektrum bei Systemen mit beliebig vielen, teils in Serie, tells parallel wirkenden, mit Reibung belasteten elastischen Zusammenhaltsmechanismen, Hel. Chim. Acta. 30, 487-493 (1947). (4) B. W. Barry and A. J. Grace, Grade variation in the theology of white soft paraffin, B.P., J. Pharm. Pharnazc., 22, 147S- 156S (1970). (5) B. W. Barry and G. M. Eccleston, Oscillatory testing of o/w emulsions containing mixed emulsifiers of the surfactant-long chain alcohol type: Self-bodying action, J. Pharm. Pharnazc., 25, 244-253 (1973). (6) S. Purwar, A. R. Padhye, and J. K. Lim, A new method of measuring the viscoelastic parameters of pharmaceutical and cosmetic semisolids, J. Soc. Cosmet. Chem., 35, 115-129 (1985). (7) O. H. Griffiths and P. C. Jost, in Spin Labeling, L. J. Berliner, Ed. (Academic Press, New York, 1975), p. 454. (8) J. H. Freed, in Spin Labeling, L. J. Berliner, Ed. (Academic Press, New York, 1975), p. 53. (9) E. Sackmann, H. Trauble, H. Galla, and P. Overath, Lateral diffusion, protein mobility, and phase transitions in Escerichia coli membranes. A spin label study, Biochem., 12, 5360-5369 (1973).

j. Soc. Cosmet. Chem., 38, 11-19 (January/February 1987) Protective value of skin tanning induced by ultraviolet radiation plus a sunscreen containing bergamot oil C. P. SAMBUCO, P. D. FORBES, R. E. DAVIES, and F. URBACH, The Skin and Cancer Hospital, Center for Photobiology, Temple University Health Sciences Center, 3322 North Broad Street, Philadelphia, PA 19140. Received August 11, 1986. Synopsis Some sunscreen formulations utilize bergamot oil to enhance tanning induced by ultraviolet radiation. To determine the tanning capabilities of such a product, and to assess the protective value of the induced tan, we chose the skin of miniature pigs to test a sunscreen-psoralen product (5% ethyl hexyl cinnamate + bergapten 30 ppm, Laboratoires Goupil S.A.). Material was applied to the skin prior to ultraviolet radia- tion exposure during the induction phase of the study, and pigmentation was assessed visually. Subse- quently, test sites were challenge-irradiated, and erythema production and sunburn cell formation were assessed. The product was effective in inducing tan without erythema, and the induced tan was effective in protecting the skin from subsequent exposure to ultraviolet radiation as assessed by sunburn cell formation. INTRODUCTION Sunscreen preparations containing bergamot oil are commercially available (1-3). This combination can be regarded as a sunscreen, protecting against acute ultraviolet radia- tion (UVR) damage, to which bergamot oil, as a source of bergapten (5-methoxypsor- alen), is added to enhance melanin production (tanning). Theoretically, the level of furocoumarin is less than that required to elicit phototoxicity, but sufficient to induce tanning. To evaluate a product of this type in an animal model, certain criteria have to be met. The model should have morphologic and physiologic characteristics similar to man, it should display tanning capability comparable to man, and there should be methodolo- gies available to assess acute damage in non-tanned and tanned skin. Recently, the skin of miniature swine has been found to meet these criteria (4). This study was designed to determine whether a bergamot oil-containing sunscreen product was effective in enhancing UVR-induced tanning of swine skin without pro- voking phototoxicity, and whether the induced tan afforded protection against subse- quent exposure to UVR. For the latter determination both erythema induction and sunburn cell (SBC) production in the epidermis were used to assess acute damage. 11