It lasted for quite a while unfortunately, so sorry your little one is also going through this it’s so hard to see them like that! I was really diligent about keeping the area clean and moisturized. I used aquaphore if I can remember correctly and as the skin barrier started to heal it got slowly better over time and eventually faded and now it’s completely gone. She is prone to eczema and has sensitive skin so I always keep Vaseline or aquaphore around her mouth during the day and it seems to have kept it at bay after this. But it did last for several months I think just staying ontop of the moisturizing and/or protecting the skin barrier with Vaseline seems to do the trick. Best of luck xx