Parrots will be parrots, first. It's unreasonable to expect them not to bite, or attempt to bite. It is a form of communication. Snickers communicated with extreme prejudice, but for a very good parrot reason.
Diffusing and essential oils have entered the companion animal arena with great success for some, and a sad end for others. The thing about diffusing essential oils is; it isn't essential. But it does require essential understanding.
I often think about the care a human needs to give themselves along with the care they give their parrot(s). I see too many people living unhealthily, and it pains me to think of what will happen to their birds once their guardians leave this life way prematurely due to nothing but their own unhealthy choices for themselves.
I like to say: eat as your parrot, and you will be fine (mostly fresh, unprocessed veggies, some fruits, nuts and clean water). And let's not forget exercising as well. It forms an equally important part of the health equation.