— § 01
What hyaluronic acid actually is.
Hyaluronic acid is a glycosaminoglycan — a long sugar polymer your dermis produces in volume — that binds many times its own weight in water. Topical HA does not refill that dermal reservoir; molecular weight prevents it. What topical HA does, well, is hold water at the corneocyte surface, plump the upper stratum corneum visibly within minutes, and make almost any active feel less harsh on the way in.
That is a useful, modest, replicable cosmetic effect. It is not anti-aging in any meaningful sense, it does not 'rebuild,' and it does not survive a dry environment without an occlusive layer above it.