What could be wrong with my pet rat?

The rat probably needs to get used to all the new smells around him.... and DO NOT use wood chips like the guy above me said, aspen and pine woodchips can cause respiratory infections and can be fatal to rats... from what ive heard fleece is fine, but make sure to clean the cage often and if the sneezing doesnt p in a week or two i'd take your pet rat to the vet