J. Cosmet. Sci., 70, 17–31 (January/February 2019) 17 Protective Effects of Sacran, a Natural Polysaccharide, Against Adverse Effects on the Skin Induced by Tobacco Smoke MOEKO DOI, YUKI SAGAWA, KYOHEI SASANO, TAKUMI TANAKA, TAEKO MIZUTANI, YURI OKANO, and HITOSHI MASAKI, DAITO KASEI KOGYO CO., LTD., Asahi-ku, Osaka 535-0005, Japan (M.D., T.T.) Department of Bionics, Tokyo University of Technology Graduate School, Hachioji-shi 192-0982, Japan (Y.S., K.S., T.M., Y.O., H.M.) Accepted for publication January 8, 2019. Synopsis Recent increases in air pollution have raised concerns about its adverse effects on human health. Sacran is a natural polysaccharide isolated from a cyanobacterium. We previously reported that sacran improves skin conditions because of its effects as an artifi cial barrier against external stimuli, which suggested that sacran might protect the skin against air pollutants. The goal of this study was to characterize the potential of sacran to protect human skin against damage from air pollutants and to compare sacran with hyaluronic acid (HA). Sacran that was topically applied on the skin stayed on the surface or in the stratum corneum. Sacran-treated fi lters had a shielding effect against benzo[a]pyrene (BaP) and aldehyde compounds contained in tobacco smoke. Sacran suppressed the upregulation of cytochrome P4501A1 messenger ribonucleic acid (mRNA), which is a xenobiotic-metabolizing enzyme induced by BaP, and other responses against tobacco smoke in HaCaT keratinocytes. Furthermore, topical application of a serum containing 0.04% sacran on the skin reduced levels of carbonylated proteins in corneocytes of tobacco smokers. Sacran showed superior effects in every characteristic measured, compared with HA. We conclude that sacran ameliorates the oxidative stress initiated by tobacco smoke by shielding the skin surface and protects human skin. INTRODUCTION Recently, the adverse infl uence of various air pollutants, such as polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds, nitrogen oxides, and particulate mat- ter, on human health has caused increased concern in the world, especially in India, China, Saudi Arabia, and African and Southeast Asian countries (1). In 2016, the World Health Organization (WHO) reported that more than 80% of people living in urban areas where air pollution is monitored are exposed to air pollutants beyond the limitations Address all correspondence to m.doi@dreamnet-daitokasei.co.jp.