Xanzer is a medium sized rat with a sweet, and loving personality. He cuddles and explores, but I have noticed lately that when I take him out for his "social time" he sneezes, a little too often for my liking. I am wondering if it is just stress? (I've had him a week, but he went to my sister's house for a day because I was out of town.) But I am also concerned that it may not be stress, but a health issue. He has no symptoms of labored breathing or discharge, but he is constantly cleaning himself (From what I've read that's fairly normal?) and sneezing. Today when he had his "out" time, he was scampering around in a panic, and sneezing up a storm. (He just came back home today.) My sister smokes (Though she doesn't smoke inside the house, the scent is still there) and they used vinegar to clean his ball.
Does that maybe, have anything to do with it? He seemed fine when he got back, but it really only started when I had him out.
*I still hear a few sneezes every couple minutes but it has greatly subsided, and he seems to be alright now....

Rats can have sensitive noses to strong scents or dust. What is his bedding in his enclosure? Is it dusty? The smoke may have caused it to be worse, though I doubt vinegar would cause sneezing.

How is he doing now? Has he gotten better?