During the winter months in northwester PA, I suffer from severe nasal congestion both day and night. I know I'm allergic to dog and cat dander, and I do own a dog and cat, that have been with me for years. Last winter I suffered from this condition and again this winter. At night my mouth is totally dry due to not being able to breathe through my nose. I've tried antihistamine medicines but nothing works. What should I do?