As it spells out clearly in the name, the Biossance Squalane + Lactic Acid Resurfacing Night Serum (£56) brings squalane (vegan, of course) into the mix of this exfoliating serum to ensure skin stays hydrated and won't get too dry or irritated overnight. The brand claims the formula is gentle enough to use every day, but we still suggest starting slow, using it two to three days a week and working your way up to more.