Unfortunately, quite a while. I have darker skin and I found that my skin had a super sensitivity to the sun and remained discolored for at least six months. Even at 1 or 2 years after the burn, it would turn different colors if exposed to the sun for any length of time, so I just learned to avoid it. I think that it ends up damaging the skin by burning it so badly as well as even the superficial nerves. Even many years later, I can still feel a bit of a difference in that area of skin when exposed to lots of sun, so I just make sure I always keep sunscreen on it. The redness did last for a bit of time as well because of the skin damage.