Parosmia and Phantosmia
Parosmia involves a distortion of the sense of smell -- the affected person reports smelling something other than the scent which is present -- for example, the person sniffs a banana but it smells like rotting flesh instead of a banana. Phantosmia involves olfactory hallucinations -- that is, there is no odorant present, but the affected person reports smelling something, usually something unpleasant.
When a normal person smells an unpleasant scent, sensory adaptation takes place rather quickly -- within a few minutes the scent seems to have disappeared. The unpleasant scents in parosmia and phantosmia can, however, be very long-lasting. Given the unpleasantness and long duration of the scents reported by those afflicted with parosmia and phantosmia, I opine that these afflictions are likely much more disturbing than is simple anosmia. In fact, I have often heard persons with parosmia or phantosmia wishing that they were anosmic instead.
Among the unpleasant scents often reported by those suffering from parosmia or phantosmia are the smells of death (rotting flesh), feces, vomit, garbage, and smoke. Research done at the Monell Chemical Senses Center has identified the smell of rotting flesh as the worst scent in the world, across cultures. Interestingly, the United States Department of Defense has a stake in this research, for the purpose of creating stink bombs.
I have heard several descriptions of the scents experienced by persons with these conditions. The one that touched me most is reproduced here: "I am afraid that this is one of the things that you just can't explain and you cannot understand unless you have experienced it. The smell is so strong and magnified and distorted that it cannot be compared with external smells, because it is coming from inside you - there is no escape. The best way I can explain it to you is that it is like a gas that is smothering you and choking you - it is overpowering to any external smells and distorts everything - it is chemical - it is rotten - it is gas like - it is moldy - it is every terrible smell all mixed together and magnified 100 times over! It makes your life miserable and takes away simple pleasures - and even when it isn't there it haunts you because you never know when it will come.
These conditions are generally thought to result from damage to the nervous tissues in the olfactory system. Such damage can result from viral infection, head trauma, surgery, and possibly exposure to certain toxins or use of certain drugs. Sometimes the condition is considered psychiatric in origin.
One potential cause of olfactory hallucinations is epilepsy. While most people think of epilepsy as involving the motor system, it does not necessarily do so. One can have epilepsy that has absolutely no involvement with one's muscles. Such epilepsy can cause hallucinations, strange thoughts, emotional feelings, etc. without any sort of muscular convulsion. If the olfactory cortex were involved, olfactory hallucinations would be present. If the visual cortex were involved, visual hallucinations would be present, etc. Reference: Focal Status Epilepticus.
I have not been able to find on the Internet much useful information about these conditions. Although I got hundreds of hits when I searched for "parosmia," most of these were pages describing various mediations (including two that I take daily) for which parosmia is listed as a possible side effect. If you find a good page on parosmia or phantosmia that you think I should link here, please let me know about it. Thanks.
Distortion of Olfactory Perception: Diagnosis and Treatment -- Chemical Senses article by Donald Leopold
Treatment of Parosmia -- includes a description of a new, minimally invasive, surgical treatment for parosmia
Contact Information for the Webmaster,
Dr. Karl L. Wuensch
This page most recently revised on 16-April-2021.