Assessing Skin Photoprotection in the Infrared Range: The Reflectance Profiles of Cold-Pressed Plant Oils

The harmful effects of solar radiation on the skin are known and scientifically proven, with recent studies indicating that not only ultraviolet (UV) radiation but also infrared (IR) radiation contributes to skin photoaging and increases the risk of carcinogenesis. Infrared radiation is also responsible for the degradation of protective carotenoids in the skin, the disruption of calcium homeostasis, and the activation of apoptosis pathways. The biological mechanisms underlying these effects include an increased level of reactive oxygen species and increased expression of metalloproteinases in the skin. The aim of this study was to evaluate the photoprotective properties of 10 cold-pressed plant oils in the infrared spectral range from 1000 nm to 2500 nm by assessing their impact on the directional–hemispherical reflectance (DHR) of human skin after their topical application. This study was conducted in vivo on the skin of 12 volunteers, with non-invasive DHR measurements taken before and directly after the application of the oil and 30 min later. Additionally, the correlation between the oil’s compounds (chlorophyll a, chlorophyll b, lycopene, and β-carotene) and antioxidant activity, expressed as the DPPH free radical scavenging capacity, was analyzed in relation to the differences in the skin’s DHR observed. An interesting result was obtained in the context of protecting the skin against IR radiation. A statistically significant increase in the skin’s reflectance after the penetration of the oil (p < 0.05) was observed in the 1700–2500 nm range for the chokeberry, fig, pomegranate, and perilla oils, suggesting their potential as photoprotective agents against IR. These findings indicate that chokeberry, fig, pomegranate, and perilla oils may serve as ingredients in cosmetic formulations designed for broad-spectrum skin photoprotection, complementing traditional UV filters with additional protection against infrared radiation. However, further research is needed to confirm these findings in a larger population.