Surely the compiler of the Animal Free Shopper left their desk for a while and a prankster just put that one in for a laugh.
But no. I've checked and it exists. It's an anal sex gland in the sense of it being a sex gland in the anus, rather than a gland for anal sex.
Appropriately enough for such black magic sounding ingredients, one contemporary perfume that uses it is Magie Noire. What chewing gum uses it? It'd certainly give a whole new meaning to 'Juicy Fruit'.
It all sounds unbelievable, but then again people think I'm making it up when I tell them the hormones for contraceptive pills come from the urine of pregnant horses kept in abominable conditions on special farms.
According to Wikipedia, not only is castoreum real but
until the 1700s, castoreum was used to treat many different ailments, including headache, fever, and hysteria. The Romans believed the fumes produced by burning castoreum could induce an abortion; Paracelsus thought it could be used in the treatment of epilepsy; and medieval beekeepers used it to increase honey production.
Whose idea was all that?
'Hmm this chewing gum's missing a certain tang. It's nice and all, but I wish it tasted a bit more like a beaver's arse'.
'This perfume evaporates a bit quickly, but hey, what can you do? Ooh, here's a thought; hold this beaver firmly and squeeze its bum all over my pulse points will you?'
Where do they get a reliable source of castoreum from? Are there farms somewhere out there? Are people breeding beavers than attacking them from behind with an apple corer?
[beaver picture courtesy of the good people at Great Plains Nature Center]