sleeping with mouth open?

i am probably overreacting to everything at this point because the vet thinks our little guy rosie may have asthma, but i have been noticing that when you are loving on him (like just now i was rubbing his ears and under his chin while he snuggled upside down in the crook of my arm) he tends to fall asleep with his mouth open a bit - not a lot, just enough that you can see his bottom teeth, and he is NOT breathing through his mouth, i have sat there with my fingers in front of his face for a few minutes making sure he is not mouth breathing.

he doesn't seem to be breathing abnormally when he does this, and he only does this is he is being loved on. is this relatively normal? the vet told me what to watch for but i worry about EVERYTHING when it comes to my babies!

All of my cats have done this at one point in their lives, it just means they are super relaxed . I wish I had a picture of her doing it but our collie mix frequently sleeps on her back with her lips flapping showing all her teeth in a great big grin! It's hilarious!

OOH! I do have a picture, she's so silly!

My Jack sometimes sleeps with his mouth open slightly, and i think it's just like humans when their relaxed and asleep, then the dribble