Sodium Hyaluronate — Frequently Asked Questions

It depends on the effect wanted, and grades span three orders of magnitude. High molecular weight material, above about one million daltons, builds viscosity and forms a surface film that reduces water loss, giving an immediate smoothing effect. Low molecular weight and hydrolysed grades give a lighter, less tacky feel. Blending two grades is common where both are wanted.

Sprinkled slowly onto vigorously moving water, or pre-dispersed in glycerine before addition. Dropped into still water it clumps immediately, forming lumps with a gelled skin that resists further hydration and never fully dissolves. Full hydration takes time rather than heat, so it is normally added during cool-down and allowed to stand.

Approximately pH 4 to 9. Outside that band, and in the presence of heat or oxidising agents, the polymer chain degrades and viscosity collapses, which is both a performance loss and a sign that the material has been damaged. Formulations combining it with strong acids, alkalis or peroxides need stability testing rather than assumption.

By bacterial fermentation, which has replaced the earlier extraction from rooster combs. Fermentation gives better control of molecular weight, avoids animal-derived material, and allows the endotoxin and protein levels required for medical device and ophthalmic grades to be met. Cosmetic, food and medical grades differ substantially in those specifications.