There was a thread on this a while ago, and unfortunately I believe the consensus was that diffusing oils is not safe for bunnies in general.
Not that they would necessarily drop dead, but certain compounds in oils can build up in their system and cause issues later, others can be very irritating to them. Buns have much more sensitive noses than we do, so that’s important to keep in mind. Even things like lavendar, which as a plant are safe, can be dangerous as an oil because they are so concentrated.
Here’s the thread from the last discussion: https://binkybunny.com/FORUM/tabid/54/aft/164918/Default.aspx
Note that one member did say they would consult their vet, but then never posted the reply.
.
.
.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.