SUBSTRATE TO MEASURE SPF 133 is readily available, and is inexpensive. In common with other in vitro substrates, how- ever, it is not a substitute for phototesting in human volunteers. ACKNOWLEDGEMENTS We are grateful to Dr. J. Ferguson for supplying many of the sunscreen products. REFERENCES (1) R. M. Sayre, P. P. Agin, G. J. LeVee, and E. Marlowe, A comparison of in vivo and in vitro testing of sunscreening formulas. Photochem. Photobiol., 29, 559- 566 (1979). (2) G. A. Groves, P. P. Agin, and R. M. Sayre, In vitro and in vivo methods to define sunscreen protection, Aust. J. DermatoL, 20, 112-119 (1979). (3) R. M. Sayre, In vitro testing of sunscreens, Proc. Proprietary Assoc., 78-85 (November 1978). (4) D. F. Robertson and G. A. Groves, The selection and use of topical sunscreens, Med. J. Aust., 2, 1445-1451 (1972). (5) G. A. Groves, The selection and evaluation of ultraviolet absorbers, Aust. J. Dermatol., 14, 21-34 (1973). (6) G. A. Groves, Evaluation of solar protective preparations, Aust. Soc. Cosmet. Chem., 90, 36-50 (1975). (7) C. Cole and R. VanFossen, Rapid in vitro evaluation of sunscreens: SPF and PFA, Photochem. Photo- biol., 47, 73S (1988). (8) S. Brown and B. L. Diffey, The effect of applied thickness on sunscreen protection: In vivo and in vitro studies, Photochem. Photobid., 44, 509- 513 (1986). (9) M. Stockdale, A novel proposal for the assessment of sunscreen product efficacy against UVA, Int. J. Cosm. Sci., 9, 85-98 (1987). (10) J. J. O'Neill, Effect of film irregularities on sunscreen efficacy, J. Pharm. Sci., 73, 888-891 (July 1984). (11) Sunscreen drug products for over-the-counter human use. Federal Register, 43, 38206-38269 (1978). (12) Evaluation of Sunscreen Products,' Experimental Dermatological Evaluation of the Protection Against Erythema of External Sunscreen Products for the Human Skin (Deutsches Institut fur Normung Normenausschuss Litchttechnik, Berlin, W. Germany 1984). (13) P. Bener, Approximate values of intensity of natural ultraviolet radiation for different amounts of atmospheric ozone. Final Technical Report DAJA3 7-68-C-10I 7, European Research Office, US Army, London (1972). (14) S. A. W. Gerstl, A. Zardecki, and H. L. Wiser, UV-B Handbook, Voll, Report LA-UR-83-728, Los Alamos National Laboratory (1983). (15) A. F. McKinlay and B. L. Diffey, A reference action spectrum for ultraviolet induced erythema in human skin. CIEJournal, 6, 17-22 (1987). (16) C. F. Dietrich, Uncertainty, calibration & probability (Adam Hilger, London, 1973). (17) R. M. Sayre and P. P. Agin, Comparison of human sun protection factors to predicted protection factors using different lamp spectra, J. Soc. Cosmet. Chem., 35, 439-445 (1984). (18) Sunscreen products--Evaluation and classification. Australian Standard 2604-1986, Standards Asso- ciation of Australia (1986).

j. Soc. Cosmet. Chem., 40, 135-139 (May/June 1989) On the comedogenic potential of quaternium-15 and DMDM hydantoin P. M. SILBER, T. J. STEPHENS, and O. H. MILLS, JR., Mary Kay Cosmetics, Inc., Dallas, TX (P. M.S., T.J.S. ), and Hill Top Research, Inc., East Brunswick, NJ (O.H.Mo). Received November 16, 1988. Synopsis The comedogenic potential of the preservatives quaternium-15 and DMDM hydantoin were determined using a rabbit ear assay. Microscopic examination of rabbit ear whole mounts indicate that these preserva- tives do not possess any significant comedogenic potential at concentrations normally encountered in cos- metic formulations. INTRODUCTION The comedogenic potential of a cosmetic raw material or cosmetic formulation is of considerable interest to the dermatologist, the acne-prone individual, and the manufac- turer of cosmetic products. Therefore it is not surprising that a "non-comedogenic" claim is associated with an ever-increasing number of cosmetic skin-care products. The potent comedogenic potential of certain cosmetic raw materials has been thoroughly discussed in the literature these include acetylated lanolin alcohols, coal tar, and iso- propryl myristate (4,7,8). However, there are many other cosmetic raw materials whose comedogenic potential has never been tested. For the most part, the comedogenic potential of preservatives used in cosmetic formula- tions remains unknown. An exception is the case of methylparaben, which has been reported to be non-comedogenic (5). Along with fragrance raw materials, preservatives as a group are among those cosmetic raw materials most frequently associated with adverse dermatological reactions such as allergic contact dermatitis (1,3). Therefore, the goal of this research was to determine if commonly used preservative ingredients may also possess significant comedogenic potential. This study examined the comedogenic potential of quaternium-15 (Dowicil 200) and DMDM hydantoin (Glydant) both preservatives are widely used in cosmetic formula- tions (2). The comedogenic potential of each preservative was determined using the rabbit ear model and sampling method described by Kligman and Kwong (6). 135