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    Jerry W. Swanson, M.D.

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Question

Phantosmia: What causes olfactory hallucinations?

What causes olfactory hallucinations (phantosmia)?

Answer

from Jerry W. Swanson, M.D.

Many people are sensitive to certain smells, but in an olfactory hallucination (phantosmia), you detect smells that aren't really present in your environment.

The odors detected in phantosmia vary from person to person and may be foul or pleasant. They can occur in one or both nostrils and usually can't be masked by food.

Phantosmia most often occurs as a result of a head injury or upper respiratory infection. It can also be caused by temporal lobe seizures, sinusitis, brain tumors, migraine, Parkinson's disease and stroke.

Because phantosmia can be an indication of a serious illness, consult your doctor if you experience such symptoms.

Note that phantosmia is different from another disorder of sense of smell, known as parosmia, in which a smell is present in your environment but is distorted. Parosmia can occur with damage to the olfactory system, such as after a severe respiratory infection. In this situation, there's usually also a loss of sense of smell.

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References
  1. Mann NM, et al. Anatomy and etiology of smell and taste disorders. http://www.uptodate.com/home/index.html. Accessed Dec. 21, 2009.
  2. Wrobel BB, et al. Clinical assessment of patients with smell and taste disorders. Otolaryngologic Clinics of North America. 2004;37:1127.
  3. Nordin S, et al. Complaints of olfactory disorders: Epidemiology, assessment and clinical implications. Current Opinion in Allergy and Clinical Immunology. 2008;8:10.
  4. Landis BM, et al. Phantosmias and Parkinson disease. Archives of Neurology. 2008;65:1237.
AN01684 March 27, 2010

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