Gentle and powerful, the Medik 8 Press & Glow Daily Exfoliating PHA Tonic With Enzyme Activator (£25) is a hydrating toner that's been formulated with polyhydroxy acid (PHAs). Given that, due to their larger molecule size, they're gentler than other AHAs like glycolic acid, it ensures surface exfoliation without ever irritating or stinging your skin. And even more clever, when applied to the skin the PHA in this specific formula converts to gluconic acid (a naturally occurring acid in your skin that both exfoliates and hydrates), which is then slowly released into the skin to ensure no irritation.