Hyponosmia

A pathological reduction in the sense of smell, characterized by decreased olfactory sensitivity due to dysfunction of the olfactory neuroepithelium, olfactory bulb, central olfactory pathways, or related structures.

Causes

• Nasal and upper airways

  • Sinusitis

  • Nasal polyps

  • Deviated nasal septum

  • Allergic rhinitis

  • Common cold

  • Influenza

  • Other upper respiratory tract infections

• Infectious causes

  • COVID-19 infection

  • Viral infections affecting the olfactory epithelium or pathways

• Neurodegenerative disorders affecting olfactory pathways

  • Parkinson's disease

  • Alzheimer's disease

• Trauma/head injury affecting the olfactory nerve

• Aging-related decline in olfactory function

• Exposure-related causes

  • Tobacco smoking

  • Toxic chemical exposure

  • Cocaine use

• Medication-related causes

  • Certain antibiotics

  • Antihistamines

  • Antidepressants

• Malnutrition

• Diabetes mellitus

• Congenital or idiopathic olfactory dysfunction

• Brain tumors affecting olfactory pathways