I have occasional problems with the cheap crappy "fresheners" the hotels use to cover up the smells that should be cleaned up. Often my eyes will water, my throat becomes dry etc. The worst situation is use of extra excessive "fresheners" to try to hide odors where a smoker puffed away in a NS room. Most chemicals used in these are naphthalene based and are very irritating in higher dosages.
The best bet is to check in early and check out the rooms. FWIW the spray used in most Holiday Inns is one of the worse irritants. I avoid them 100%.
MisterNice