Is hyaluronic acid really as good as it is being made out to be or is it just hype. Can the molecule penetrate into the skin or is it like collagen and too big to get in.
The hyaluronic acid used in cosmetics has been hydrolysed so the molecule has been split up into small chunks that have a chance to get into the skin. It does seem to have a moisturising effect but I am not sure that there is any particularly good reason to chose it over other less glamorous and frankly much cheaper alternatives.
There is a lot more detail about hyaluronic acid and other humectants here.