An exopolysaccharide (complex sugar) designed to prevent pollution-induced irritation and premature ageing. This ingredient is marine-derived and sustainably harvested from microbes in a unique ecosystem in French Polynesia. Alteromonas ferment extract is fully compatible and biomimetic with human cells and naturally shields the skin against urban pollution and smog by chelating heavy metals and providing a barrier against hydrocarbon absorption through the skin. It also reduces the absorption of barrier damaging fine particulate matter in smog (PM2.5) and works to neturalise resulting free radical damage.