Table 1

Causes of loss of smell

ConductiveSensorineural
Common causes
Allergic rhinitis
Rhinosinusitis with or without nasal polyposis
Illicit drugs including cocaine
Septal deviation (causing complete loss of smell is rare, would typically associate with unilateral nasal obstruction)
Post-viral
Neurodegenerative disorders including Parkinson’s, Alzheimer’s diseases
Psychiatric disorders (depression, bipolar disorder, schizophrenia)
Head injury
Less common causes
Systemic diseases with nasal manifestations, eg, granulomatous with polyangiitis
Iatrogenic (nasal surgery, laryngectomy, medication)
Central space occupying lesion
Heavy metals and solvents (cadmium, iron, zinc, ammonia)
Congenital (Kallmann syndrome)