If you are worried about mites, try this. Get a plain white paper towel and spray it so it's damp. Not wet, just damp. Then wrap it wround him, behind the neck and get him to go through it like he is passing through a hole. Your hand will be the tunnel.... when he has passed through it, look at the paper.... if there mites on him... then you will see them on the paper. Also check the crease under his lower jaw. Mites like that spot.
It doesn't sound like mites, but try that. It might also bring some piece of mind to you also.