my nine year old daughter came home from school with a very itchy red welt on her arm about the size of a silver dollar,, last week she got one on her hand. I thought it was just a bug bite.. now she tells me the teacher saw mice droppings in her classroom and the janitor put down traps. She only has the one mark,, this time her arm last time her hand. It doesn't hurt but itchies something awful. What could this be?