Several years ago a French cosmetic chemist wanted to know why nothing grows under oak trees when there are black truffles growing in the soil. An extract from the truffles was found to inhibit plant growth under the oak trees and it is this same extract which was later found to inhibit hair regrowth after waxing.
The extract does not make the deodorant smell of truffles though, a combination of essential oils give a fresh floral scent.