Protection from Near-Infrared to Prevent Skin Damage

Over half of the solar energy consists of near-infrared, and in addition to natural near-infrared, humans are increasingly exposed to artificial near-infrared from electrical appliances. Thus, we are exposed to tremendous amounts of near-infrared. Despite the wide prevalence of a variety of ultraviolet blocking materials, the necessity to protect against near-infrared has not been well recognized. To clarify the necessity to protect against near-infrared, we assessed cell viability of human fibroblast cells after water-filtered broad-spectrum near-infrared (1100 1800 nm together with a water-filter that excludes wavelengths 1400 1500 nm) treatment using 2 sets of transparent polycarbonate plates, one to block ultraviolet and the other to block both ultraviolet and near-infrared. The cell viability was significantly decreased after 10 rounds of near-infrared irradiation at 20 J⁄cm2 in near-infrared treated cells without a protective polycarbonate plate and near-infrared treated cells using the polycarbonate plate to block only ultraviolet. Assuming that the cell viability of the non-irradiated control to be 100, the cell viability of the near-infrared treated cells without any protection was 0.2. The cell viability of the near-infrared treated cells with the polycarbonate plate to block only ultraviolet was 0.3, whereas both ultraviolet and nearinfrared protected cells retained a viability of 85.1. The results of this study indicate that protection from not only ultraviolet but also near-infrared should be considered to prevent skin damage.