Mannitol

Mannitol is a sugar alcohol used mainly as a humectant/osmolyte and stabilizer in leave-on products, typically at low-to-moderate percentages, and it is generally well-tolerated in human patch testing with very low irritancy. While not completely inert (rare stinging can occur on severely compromised or fissured eczema skin due to osmotic effects), it is considered exceptionally gentle and appropriate for highly sensitive skin when properly formulated. Safety Notes: In commercial skincare, mannitol most often appears at very low levels (around 0.01–0.3%) as a humectant/tonicity agent and stabilizing excipient in leave-on serums, essences, and some dermocosmetic soothing formulas. Higher-use products (typically 1–5%) are seen where mannitol is used more deliberately as a polyol humectant/bulking agent, especially in hydrating leave-on creams/gels and some masks. The upper end observed in OTC consumer-available products is around ~10% in high-polyol, water-based hydrating gels/ampoules and sheet-mask essences, where texture, tack control, and water activity management allow higher solids without prescription-only context.