[cypher]

Really glad to hear you were able to find a better vet & get him seen, I hope he improves now with the meds.
It's never easy to say for sure about allergies but they aren't really all that common & the new substrate really doesn't sound like something he'd be allergic to unless the cotton in it is causing him a problem, I've never seen that substrate so it's hard to say for sure. It's possible there was something in there that shouldn't have been that caused a. problem & stress may have been a factor again it's never easy or even possible to be sure about some of these things.
If you are still concerned about the substrate if you can get kaytee clean and cosy where you are that is probably about the best, just plain soft paper, not dusty & nothing to cause any kind of reactions.