Wow! I’m happy to find this… my boys are 14 and 12 get these each year. They either have it on their chest or back. When I catch it I take a picture since they don’t come with any symptoms, I’m not sure how often they get them. Here is one from June 27th. Their pediatrician thought they were laying on something to get the marks, but we knew they did not. We live in Boston. I hope we can figure this out!