Phantosmia (phantom smell), also called an olfactory hallucination or a phantom odor^[1] is smelling an odor that is not actually there. It can occur in one nostril or both.^[2] Unpleasant phantosmia, cacosmia, is more common and is often described as smelling something that is burned, foul, spoiled, or rotten.^[3] Experiencing occasional phantom smells is normal and usually goes away on its own in time.^[4] When hallucinations of this type do not seem to go away or when they keep coming back, it can be very upsetting and can disrupt an individual's quality of life.^[2]