Enhancing Photoprotection: Assessing Visible Light Photoprotection in Tinted Inorganic Sunscreens

Visible light (VL, 400-700 nm) and long wavelength UVA1 (VL + UVA1, 370-700 nm) have been reported to cause erythema in light skin phototypes, Fitzpatrick skin types I-III (FST I-III), and to exacerbate pigmentary dermatologic conditions (e.g., melasma, hyperpigmentation, post-inflammatory hyperpigmentation) in individuals with dark skin phototypes (FST IV-VI). Until recently, limited options existed for photoprotection against VL + UVA1, including tinted formulations containing iron oxides (Fe₂O₃) or pigmentary titanium dioxide (TiO₂), as well as antioxidant-enriched sunscreen systems. Zinc oxide (ZnO) and TiO₂ are often utilized in the development of mineral-based (inorganic) sunscreens as the active ingredients to protect against broad spectrum Ultraviolet (UV) radiation via their absorption properties. However, some of these products often leave a white cast, particularly on dark skin, making these products unfavorable, altering skin tone appearance leading to concerns for sunscreen compliance. Tinted sunscreens (Fe₂O₃) are designed to enhance cosmetic elegance and improve compliance across diverse skin tones. This study aims to evaluate the photoprotection properties of a novel Zn-based inorganic tinted sunscreen enriched with five antioxidants (5 AOX) against VL + UVA1 induced biologic effects (hyperpigmentation and erythema).

Twelve healthy adult subjects with FST IV-VI were enrolled and the effectiveness of the new Zn/Fe₂O₃/5 AOX sunscreen, compared to several commercially available tinted and non-tinted mineral sunscreens, was evaluated. The erythema and pigmentation assessments were performed by diffused reflectance spectroscopy (DRS), polarized photography, and investigator global scoring immediately, 24 h, and 7 days after irradiation (320 J/cm²).

DRS results demonstrated that the novel Zn/Fe₂O₃/5 AOX effectively reduced immediate erythema and pigmentation as well as delayed pigmentation when compared with formulas containing ZnO only (p < 0.05). Not all inorganic/Fe₂O₃ formulas significantly reduced erythema and pigmentation induced by VL + UVA1 when compared with the ZnO only formula.

These results highlight the enhanced effects of 5 AOX-enriched tinted mineral sunscreen to be photoprotective against VL + UVA1, with a blendable tint designed for use on skin of all colors aimed at improving patient compliance and overall sunscreen use.