[cypher]

I’m not aware of any scientific studies but I think it would be unlikely to be considered as a subject for scientific study really, are you looking for references to show people maybe?
I think it’s just one of those common sense things if you understand hamster behaviour & their need to scent mark their territory without having to compete with something smelly we put in the cage1
In addition to possible respiratory issues there may also be issues with constantly rubbing against things to scent mark & over grooming to spread their scent around.