FOREO's Serum Serum Serum helps to keep skin looking youthful. It deeply hydrates and locks in moisture with hyaluronic acid. Infused with squalane, this serum balances oil production and enhances the skin’s natural defenses. Lightweight and nourishing, it glides over the skin to rejuvenate and restore the complexion. Created to fight premature signs of aging, skin is left brighter, softer, and smoother.