Just as a PSA: keep essential oil diffusers away from your cats! I don’t imagine dogs would benefit either but cats can be fatally poisoned very quickly with an oil diffuser in the room.
http://artsyfartsylife.com/cats-essential-oils-dont-mix/
http://www.vetstreet.com/our-pet-experts/do-essential-oils-pose-a-risk-to-pets