Hyaluronic acid (sometimes listed as sodium hyaluronate or glycosaminoglycans) has been around for yonks - it's not a new sensation and when we're young and sprightly, we make buckets of it on our own - producing it to lubricate our joints, keep our skin plump and even keep our eyeballs ball-y (*shudder*).

However, as with most fun things, hyaluronic acid levels naturally deplete as we grow older (from around 18) although the side-effects don't usually expose themselves until we've made it safely to our mid-to-late 30s (still too soon), which is why it's important to top-up the tank.

Hydrophillic (water-loving), hyaluronic acid attracts up to 1000 times its molecular weight in water, making it amazing at keeping skin hydrated - and in turn, a brilliant youth-boosting hero; water keeps cells 'plump' and cellular walls rigid, to diminish the appearance of wrinkles, and maintain skin's fullness and firmness.

In the olden days (the noughties), you could purchase all manner of hyaluronic acid-rich treatments but, due to the size of the molecules, these serums couldn't penetrate the skin so simply sat on top, then got washed off. Nowadays, chemists and dermatologists have got wise, and are producing treatments which deliver this skin-plumping youth dew directly to where it's most needed - blending hyaluronic molecules of different sizes, to maximise the hydrating effect.

Ideal for quickly lessening fine lines and crow's feet, as well as supplementing your skin's lipid barrier to prevent moisture loss (especially important if your skin is dehydrated or you work in water-leeching air-conditioned offices), hyaluronic is pretty much 'one size fits all'; a humectant (not emollient) hydrator, this makes a great {serum} for dry skins but won't suffocate congested or combination {complexions}.

Serums (such as Dr. Dennis Gross Skincare's {Hyaluronic Marine Hydration Booster}, or {The Ordinary}'s ultra-light, non-tacky {Marine Hyaluronics}) have a featherweight formula - absorbing within seconds to flood skin with a thirst-quenching drink of water. If you mist your face first (Allies of Skin's {Molecular Saviour Mist} is essentially a nutrient and moisture reservoir) you'll further optimise the serum's plumping properties by providing a wealth of precious moisture for the HA molecules to cling to.

If however, you need to see an impact FAST try Dr. Dennis Gross Skincare's {Hyaluronic Marine Hydrating Modeling Mask} which stars hyaluronic acid alongside potent minerals and microelements to provide both immediate and long-term benefit. Or try Saturday Skin's {Quench Intense Hydration Mask} - a sheet mask that's brimming with essence to act like a long drink of water for thirsty complexions. The HA 'swells' cells to help make you look younger in minutes, while a cocktail of skin conditioning, protective and reparative ingredients works to 'undo' signs of damage and help optimise skin's cellular efficiency.

HOW TO USE