Last revised by Rohit Sharma on 6 Apr 2022

Anosmia (also known as anosphresia or olfactory anesthesia) is the complete absence of the sense of smell. 

In addition to anosmia, there is also hyposmia (a.k.a. microsmia or olfactory hypoesthesia) representing a diminished sense of smell and parosmia (a.k.a. dysosmia or paraosmia) referring to any pathology of the olfactory system 1,5. Phantosmia is the experience of a smell being present without an actual stimulus, i.e. an olfactory hallucination 5. For completion, normosmia is the state of having normal olfactory function.

It is estimated that the point prevalence of an impaired sense of smell is as much as 19.1% adult population and four-fifths of over 75-year-olds 2.

The underlying causes of anosmia have been traditionally subdivided into 2,5:

  • conductive: an obstruction to the passage of odorants, or
  • sensorineural: dysfunction of the olfactory neurons or olfactory nerve (I)
  • central: dysfunction of the olfactory processing systems of the CNS



  • systemic pathologies with olfactory complications, e.g. granulomatosis with polyangiitis
  • postoperative, for example nasal surgery
  • medications, e.g. antibiotics (aminoglycosides, penicillins, macrolides, tetracyclines), amino ester anesthetics (e.g. procaine), propylthiouracil



It is increasingly clear that this anatomical approach to the etiology of olfactory dysfunction is limited, and ultimately unhelpful, as underlying diseases, e.g. chronic rhinosinusitis, may cause loss of smell via both obstructive and neural mechanisms 5.

Anosmia is derived from Classical Greek roots. "οσμη" (osme) means an aroma/scent, and "αν" (an) is a prefix used to indicate negation 4.

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