Loss of Smell: Causes, Evaluation and Treatment

A reduced sense of smell is called hyposmia, while complete loss is called anosmia. Smell can be affected when odours cannot reach the smell area because of nasal swelling or blockage, or when the smell nerves and pathways are damaged. Common causes include viral respiratory infections, allergic rhinitis, chronic sinusitis, nasal polyps, ageing, head injury, smoking and certain medicines. Less commonly, smell loss may be associated with neurological disease or a nasal growth. Many people who report loss of taste actually have reduced flavour perception because smell contributes strongly to flavour. Evaluation includes the timing and pattern of symptoms, examination of the nose and sometimes nasal endoscopy or formal smell testing. Imaging may be considered when loss is one-sided, follows significant injury, has no clear cause or is associated with neurological or suspicious nasal findings. Treatment targets the cause. Allergy or inflammatory sinus disease may improve with appropriate medical therapy. Polyps or structural blockage may require additional treatment. Smell training involves repeatedly smelling a set of familiar scents over many weeks or months and may help recovery in some cases, particularly after viral smell loss. Steroid medicine should only be used when clinically appropriate and under medical guidance. Smell loss affects safety. Patients should ensure smoke and gas alarms work, check food expiry dates and be cautious with spoiled food. Seek prompt evaluation when loss is sudden without a clear respiratory illness, is one-sided, follows head injury or occurs with neurological symptoms, severe headache, facial numbness or persistent bleeding.