REACTIVITY OF SUNSCREEN COATINGS 135 REFERENCES (1) J. C. Ireland, P. Klostermann, E. W. Rice, and R. M. Clark, Inactivation of Escherichia coli by titanium dioxide photocatalytic oxidation, App/. E,v. MicrobioL, 59, 1668-1670 (1993). (2) H. Matsubara, M. Takada, S. Koyama, K. Hashimoto, and A. Fujishima, Photoactive TiO 2 containing paper: Preparation and its photocatalytic activity under weak UV light illumination, Chem. Lett., 767-768 (1995). (3) M. Biguzzi and G. Shama, Effect of titanium dioxide concentration on the surviving of Pseudotoo,as stutzeri during irradiation with near ultraviolet light, Lett. AppL Microbial., 19, 458-460 (1994). (4) M. Kobayashi and W. Kalriess, Photocatalytic activity of titanium dioxide and zinc oxide, Cosmet. Toiletr., 112, 83-86 (1997). (5) E.G. Janzen, Spin trapping, Acc. Chem. Res., 4, 31-40 (1971). (6) K.T. Knecht and R. P. Mason, In vivo spin trapping of xenobiotic free radical metabolites, Arch. Biochem. Biophys., 303, 185-194 (1993). (7) X. Shi, Generation of SO•' and OH radicals in SO32- reactions with inorganic environmental pollutants and its implications to SO32- toxicity, J. Inorg. Biochem., 56, 155-165 (1994). (8) H. M. Swartz, and T. Walczak, In Vivo EPR: Prospects for the '90's, Phys. Med., 9, 41-48 (1993). (9) H. M. Swartz and T. Walczak, An overview of considerations and approaches for developing in vivo EPR for clinical applications, Res. Chem. Interreed., 22, 511-523 (1996).

j. Cosmet. Sci., 49, 137-139 (March/April 1998) Letter to the Editor TO THE EDITOR: The topic of irritation of personal care products is a very important one to the formu- latot. In this regard, the article by M. M. Rieger on the skin irritation potential of quaternaries (J. Soc. Cosmet. Chem, 48, 307-317 [1997]) is very timely in addressing the concept of irritation, specifically the concept that irritation of a formulation is not merely the result of the selection of one of the molecules chosen for inclusion in the formulation, but is dependent upon all components in the formulation. Other ingredi- ents will affect skin penetration and other functional attributes of the formulation, which in turn have a tremendous effect upon irritation of the entire formulation. Dr. Bill Wade of the University of Texas at Austin has consistently pointed out that no surfactant is inherently water-soluble or water-insoluble, solubility in water and other surfactant properties in the formulation being intimately connected to the other com- pounds in the formulation. We have observed in our development work that Dr. Wade's comments are equally valid for irritation properties as well as for more traditional surfactant properties. SILICONE COMPLEXES OF QUATS An example of this phenomenon is shown in the fact that we have determined that forming a complex between a carboxy functional silicone and traditional quats signifi- cantly reduces the negative attributes of many irritating quats. Steara/konium chloride is an excellent conditioning agent, having outstanding substan- tivity to hair. It has detangling properties, improving wet combing when applied after shampooing. The FDA formulation data for 1976 reports the use of this material in 78 hair conditioners, eight at less than 0.1%, eighteen at between 0.1% and 1.0%, and 52 at between 1% and 5%. Cety/trimonium chloride, or CTAC, is a very substantive conditioner that, in addition to having a non-greasy feel, improves wet combing and also provides a gloss to the hair. It is classified as a severe primay eye irritant. Therefore, its use concentration is generally at or below 1%. When these traditional quats are combined with a stoichiometric amount of a new carboxy silicone, covered by various U.S. Patents (1,2), many desirable effects occur. The complexes have improved water solubility, are better conditioners that are more uni- formly applied to hair and skin, and are minimally irritating to the eyes. 137