Aspen is the worst bedding... Other beddings wreak havoc even with benedryl. Ironically enough, I don't have urine soaked mice, and they don't walk in their droppings/urine. So far, there haven't been any problems and my mice are just as clean as mice that have bedding. They don't have the pleasure of burrowing through bedding though, but, if I were to use Yesterday's News, they wouldn't be able to anyways. As I said in a previous post, I don't have problems with puddles all over the place or running into their play area.