"When I prescribe clinical strength retinol, skin purging happens all the time," explained Dr Wedgeworth. "I really have to warn people, but I always tell my clients that they’ll get there – it’s just all this congestion coming out." By congestion, Dr Wedgeworth means spots – and quite possibly lots of them. "Vitamin A is very good at dissolving away comedones, which are blocked pores clogged with things like oil and keratin," explains Dr Wedgeworth. They can be 'closed' (flesh coloured bumps) or 'open' (blackheads, whiteheads and small red bumps). "Once that whole process is happening, skin becomes more inflamed and red because the skin recognises that something is changing, and so makes those little bumps into bigger, redder ones. Where people hadn’t noticed blocked pores under the skin so much, suddenly they notice them tenfold. For some people it can be really active, but it settles after that stage, so I always warn people that when it comes to acne, things get worse before they get better."