Sorry, I missed the update....CO poisoning sounds like a strong possiblity, or perhaps an allergic reaction to fragrance, esp. the new Tide scents and Febreze. Is there improvement when he gets into the shower??? Also, make sure he bathes with just water, no scented shampoos, etc., and if there's improvment, then follow the sinus and the scent-sensitivity trails. Both my daughter and grandson have scent sensitivities, just like me....