Skin Hyperpigmentation after Cryotherapy for Wart Removal

A few years ago I performed cryotherapy on a teenager to remove some warts on his knees and elbows. A several days later I got a call from his mother because of darkening of the skin around the areas that I froze.

There were even some patches near but not connected to the areas that I froze.

This was the first time I had seen this complication, but I explained to the mother that this is something that can happen with cryotherapy. It usually only lasts a few months but can last longer. I am not exactly sure how long it lasted in this case but it wasn't very long. I have seen this young man many times since then and it was never an issue again. I spoke with my fellow blogger Joe about this and he told me to have the patient use sunscreen over the areas (right Joe?) when out it the sun, which I did do. I haven't really been able to find any literature that supports that practice but it is something to try.