What is it actually? Big, scientific word coming up here, but hyaluronic acid “is a glycosaminoglycan, similar to those naturally found in skin,” says John. Glycosaminoglycans help moisturise skin by keeping water in, but as we get older, the amount of glycosaminoglycans nose dives and skin tends to become drier, he explains.

Why is it beneficial? It’s a super moisturiser providing effective replenishment of lost moisture, says John. Sonnette agrees; it literally ‘quenches’ a thirsty skin, she says. If you want to be really clever, research the molecular weight (how much a substance weighs) of the hyaluronic acid in the product you’re investing in. Want hydration that goes deep into your skin? Make sure the ingredient is of a low molecular weight. “Lower molecular weight hyaluronic acid penetrates deeper into the skin and is able to provide moisture deeper in the epidermis,” says John. A higher molecular weight hyaluronic acid tends to provide a film of moisture on the skin, he adds.

Who should use it? Parched skins! And, because hyaluronic acid moisturises the skin without any oil, a dehydrated, oily skin will benefit greatly from this ingredient too, says Sonette.

Your miracle potion? The face is one area of your body you may not mind looking plump. Sagging, sunken skin makes one look, well, old. Combat face fall with Optiphi’s Intense HA Serum that can be used daily under your moisturiser. It’s been formulated to re-plump and intensify skin hydration on a cellular level (in other words, deep down), meaning it gives dehydrated, structurally weak skin a whole lot of love.