Even the most tolerant pets should only be exposed to diffused essentials oils for a few minutes, preferably in a different room. The oils should be heavily diluted to avoid concentrations that are toxic. Common Diffuser Essential Oils that may be Toxic to Dogs, Cats, Rabbits, Birds, Fish, Reptiles and Small Pets. This is not a comprehensive list of all essential oils that may be toxic to pets, but it does cover some of the most popular diffuser oils. Wintergreen Peppermint