Melatonin skin penetration and circadian repair pathway Animated cross-section: melatonin penetrating skin layers, activating MT1/MT2 receptors, upregulating antioxidant enzymes, and triggering the 10 ROS cascade. STRATUM CORNEUM lipid barrier EPIDERMIS keratinocytes · MT1/MT2 DERMIS fibroblasts · collagen MELATONIN 0.5% MT1 MT2 SOD GPx CAT Amphiphilic penetration Both water- and fat-soluble. Crosses the lipid-rich stratum corneum without a carrier system. Unlike purely water- or oil-soluble actives, melatonin crosses both compartments. Receptor-mediated signalling MT1 and MT2 receptors in keratinocytes activate downstream repair gene expression overnight. Skin synthesises its own melatonin — Slominski et al. Antioxidant enzyme upregulation Upregulates SOD, catalase, and GPx — the skin's endogenous antioxidant defence enzymes. Fischer TW, Kleszczynski K. Dermato-Endocrinology 2012. The 10 ROS cascade Melatonin → AFMK → AMK. Each metabolic step neutralises further reactive oxygen species. One molecule. Ten reactive species cleared — Reiter RJ et al. Represents published ingredient research. HelioRhythm Night Serum has not been independently clinically tested. Slominski AT et al. · Fischer TW, Kleszczynski K · Reiter RJ, Tan DX · Dreher F et al.