Bathing your ferret is only recommended when they are so incredibly filthy that a bath is absolutely necessary. Covered in tar being a good example of absolutely necessary. The reason for this is that ferrets secrete an oil all over their body to hydrate their skin and keep it healthy. When you bathe a ferret, this naturally occurring oil is washed away and the body then kicks up production. If you wash your ferret too often, the oil production goes into overdrive causing the musky odor normally associated with ferrets to become much stronger.