Hyaluronic acid naturally occurs in human tissue. At the epidermal level, it ensures proper hydration, boosts circulation and encourages cell renewal. In the dermis, it inflates the extracellular matrix, acting as a binding agent between elastin and collagen fibres. It also helps the body to synthesise these two molecules, giving the skin a smooth, firm appearance. As we age, the synthesis of hyaluronic acid is greatly diminished and is of poorer quality. To make up for the ensuing loss of firmness, make sure your anti-ageing skincare is packed with this key ingredient. Look out for it in serums, moisturisers and face masks.