Because Hyaluronic Acid is a naturally occurring substance, it is easily accepted by the skin, does not cause irritation and can be used by everyone. Its function in the skin is to retain moisture. This keeps your skin hydrated, plump and healthy. As you mature, your own levels of Hyaluronic Acid dissipate, which leaves your skin looking tired, creepy and dehydrated. This is why it is important to add Hyaluronic Acid to your skin care regimen.