I also felt like my skin had become a little sensitive to the 10% lactic acid serum I've been using (characterised by flakiness and tightness) and so swapped it out for the PHA Plus Serum, £14 , in the evening. PHAs, or polyhydroxy acids, break down the paste-like mixture of oil and dead skin cells before they can cause blockages and inevitably breakouts, but thanks to their large molecular structure, they're a little gentler on skin than AHAs or BHAs, making them better for reactive skin types. The result? Fewer clogged pores and less irritation than before. In my opinion, definitely give GoW a go if you have any skin bugbears. Here's what's worth buying.