I see that some readers are not familiar with the lessons on cedar toxicity.
Cedars shavings are a no-no for ferrets.  The acids in cedar can cause
irreversible damage as I understand it to the central nervous system.
Therefore why would you use a shampoo on ferrets with cedar in it.  The
toxicity is from cedar being absorbed into the bloodstream through pores of
the skin, so if you are shampooing your ferret with a shampoo with cedar
oils in it it will also enter into the bloodstream through their pores.
Perhaps you should reconsider on this?
[Posted in FML issue 1691]