My Pidgie has sinusitis but I don't know if it's the same as rhinosinusitis. She was put on an antihistamine which made her quite jittery and caused her to wail, so I took her off it. My vet also gave me Viralys and he told me to buy some saline solution and squirt it into her nostrils. Pidge's got so bad that she had a couple of nosebleeds and it all started from a paint allergy, so Jen may be on the right track. Good luck w/this and perhaps give the saline solution a try. Keep us posted.