IOPE Retinol Expert 0.1%

IOPE Retinol Expert 0.1% is the lowest rung of a three-strength ladder — the brand also makes it at 0.3% and 0.5% — and it is the one Korean shoppers are pointed at first. The standing advice in Korean write-ups is unambiguous: if you have never used retinol, start here, and this is also the largest bottle of the three at thirty millilitres.

Korean name: 아이오페 레티놀 엑스퍼트 0.1%
Size: 30ml