Leela.. mint is not by default toxic to gliders, catnip and catmint are the only 2 which are.
That being said, essential oils are concentrate (when they are real essential oil, most of the things sold in north america under that name are in fact perfume extracts, which is not the same thing) and even for human, it is not advised to be in physical contact with pure oil, so I guess you would not want to take any risk of contact.
I do use both mint, teatree and eucalyptus oils without issues, but only a few drops a day in the air purifier, never more