Sunscreens and vitamin E provide some protection to the skin immune system from solar-simulated UV radiation

Previous studies have indicated that sunscreens designed to protect from erythema do not adequately prevent immunosuppression. Mice were irradiated with suberythemal doses of solar-simulated ultraviolet radiation (ssUVR) to assess the immunoprotective ability of sunscreens. Whereas C3H/HeJ and BALB/c mice had similar sensitivities to ssUVR-induced inflammation, C3H/HeJ mice were more sensitive to ssUVR-induced immunosuppression. Octyl dimethyl-p-aminobenzoic acid did not protect from immunosuppression and, thus, had an immune protection factor (IPF) of 1. 2-Ethylhexyl-p-methoxycinnamate and microfine titanium dioxide provided limited protection, both having IPF values of 1.127. Immune protection by the sunscreens appeared to be dependent upon absorption of UVA as well as UVB, and was much less than predicted from the sun protection factor. Vitamin E, an inhibitor of lipid peroxidation, also protected the immune system, with an IPF of 1.2, indicating that oxidation of lipids is involved in UVR-induced immunosuppression, and that it should be possible to develop sunscreens which protect the immune system.