This paper studies the peroxidation of linoleic acid and of porcine skin lipids upon UVB irradiation, in the presence of various TiO2 specimens used as inorganic sunscreen pigments in different emulsion systems. It was found that different TiO2 specimens induce quite variable lipid peroxidation in the same emulsion system, which suggests that the different coatings widely differ in their effectiveness to lower the photocatalytic activity of TiO2. However, it was also found that the extent of lipid peroxidation caused by the same TiO2 pigment in different emulsions was even more variable than the effects of different pigments in the same system. This finding might imply that the choice of the formulation components different from TiO2 could be of paramount importance as far as the potential skin damage induced by the photocatalytic activity of TiO2 is concerned.