Oh my God, sprik, that's really scary! How old is your ex? 8, perchance? What a total idiot. He needs someone (maybe not you, I don't know) to give him a long, hard talk about parental responsibilities. Whether he remember she was allergic or not is not the issue here (although obviously an issue as he should have remembered), the issue is that he didn't even call you or anyone else to check. Frivolousness is not a trait of the good parent.