Commercial sunscreen formulations: UVB irradiation stability and effect on UVB irradiation-induced skin oxidative stress and inflammation.

Evidence shows that sunscreens undergo degradation processes induced by UV irradiation forming free radicals, which reduces skin protection. In this regard, the biological effects of three commercial sunscreen formulations upon UVB irradiation in the skin were investigated. The three formulations had in common the presence of benzophenone-3 added with octyl methoxycinnamate or octyl salycilate or both, which are regular UV filters in sunscreens. The results show that formulations F1 and F2 presented partial degradation upon UVB irradiation. Formulations F1 and F2 presented higher skin penetration profiles than F3. None of the formulations avoided UVB irradiation-induced GSH depletion, but inhibited reduction of SOD activity, suggesting the tested formulations did not present as a major mechanism inhibiting all UVB irradiation-triggered oxidative stress pathways. The formulations avoided the increase of myeloperoxidase activity and cytokine production (IL-1β and TNF-α), but with different levels of protection in relation to the IL-1β release. Concluding, UVB irradiation can reduce the stability of sunscreens, which in turn, present the undesirable properties of reaching viable skin. Additionally, the same SPF does not mean that different sunscreens will present the same biological effects as SPF is solely based on a skin erythema response. This found opens up perspectives to consider additional studies to reach highly safe sunscreens.