Remember, if YOU can smell anything bad, the odor is 100X stronger for a rat’s finely-tuned sense of smell. Every time you clean their odor off of everything, they’re just going to go crazy and try to remark everything. Rats are not smelly animals. Either their cage or tank is retaining smells, or your rat has an infection or sickness causing it to smell. Reducing Pet Rat Smell. Smelly rats are most often caused, unintentionally by insufficient care and cleaning. The so called smell is usually ammonia from their urine which can be quite pungent when left for long periods. If you are super cleaning the cage EVERY time you swap out the bedding, you should probably stop doing that. You’re probably already well aware that odors can cause significant health problems for pet rats, especially if the smell is due to urine buildup. Pet rats belong to the species Rodentia, meaning "to gnaw" in Latin, because of their teeth that grow longer throughout their lifetime. The urine smell you mention is a byproduct of infrequent or inadequate cage cleaning, and this can be mitigated by a good cleaning regimen. It is possible to reduce rat smells through simple actions. Rats like for their homes to smell like them. The rat itself does not usually have an odor, but picks up smells from his environment. Rats like to groom themselves and stay clean. If they do smell bad, it is most likely one of two things. They are actually extremely clean animals and should not smell bad at all. Rats always have a mild musky (almost like grass-like) scent to them, which I personally don't find offensive; I think it's kinda cute actually.