Typically used at 0.1-2%. Hyaluronic acid is not readily soluble in water as it binds water very quickly forming a gel. Hyaluronic acid needs to be carefully sprinkled into the water under constant high-speed stirring (preferably with a hand mixer or vortex mixer). The mixture starts then thickening quickly and becomes a gel. At the point no additional hyaluronic acid can be added as there is no water left for hyaluronic acid to be dissolved in (additional hyaluronic acid would only form lumps).