Went to a water park with family two days after our 13-month-old got shots ( MMR , chicken pox , and one more). Although they looked a little different, both our 13-month-old and her 20-month-old cousin got rashes on their legs/butt, although we thought they looked like an allergic reaction to sunscreen (although they were two different types of sunscreen. The 20-month-old seemed more bothered by the heat, and the next day we went to the same waterpark again. It wasn t until a day or two later that we noticed our 13-month-old s red spots had changed from looking like an alleric reaction/poison ivy almost raised area to being a lot of dots over her legs and butt. Our in-laws reported that the 20-month-old had a similar rash (we did not see it to know it to be the same), but that it cleared up in a few days; however, the 20-month-old s 4-year-old sister got a similar rash bumps on her legs and bumps. Our 3-year-old has not developed a rash of any kind at all, but now that we are a week away from the water park, we re concerned about what it is and if this is not something that will run its course as it appeared to with our 20-month-old niece. We tried cortisone at the end of last week, and that seemed to do nothing; we used baby benadryl , but that just seemed to keep the baby awake; we gave some baby tylenol while she had the fever, but apart from a couple days after getting home from the water park, she doesn t seem to have a fever, although she doesn t seem to be feeling great; we have used calamine lotion, but she isn t itching at anything a whole bunch, but since the calamine lotion seems to be drying out the bumps and perhaps the situation is improving, we have continued to do that.