phantosmia

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

Olfactory hallucinations can be caused by common medical conditions such as nasal infections, nasal polyps, or dental problems. It can result from neurological conditions such as migraines, head injuries, strokes, Parkinson's disease, seizures, or brain tumors. It can also be a symptom of certain mental disorders such as depression, bipolar disorder, intoxication or withdrawal from drugs and alcohol, or psychotic disorders. Environmental exposures are sometimes the cause as well, such as tobacco smoke, exposure to certain types of chemicals (e.g., insecticides or solvents), or radiation treatment for head or neck cancer.