What should you know about flu and loss of smell?

Loss of smell can happen when congestion, mucus and inflammation prevent aromas from reaching smell receptors high inside the nose. Food may then seem bland because smell contributes strongly to flavour. Flu can do this, but a common cold, allergic rhinitis, chronic sinusitis and COVID-19 may also cause a change. Some people notice altered smell after the blocked nose improves. A smell change by itself cannot identify which infection or condition is responsible.

Rest, drink enough fluid and use saline nasal spray or rinsing only as directed and with safe water. Avoid smoke and strong irritants. Check food dates carefully because smell may not warn you about spoiled food, and use working smoke and gas alarms. Do not place essential oils or other products inside the nose. Follow current local advice about testing and reducing contact with others when respiratory infection is possible.

Seek urgent help for breathing difficulty, confusion, severe headache with neck stiffness, or a head injury followed by smell loss. Arrange a clinician review if the loss is sudden without congestion, lasts after the respiratory illness has settled, returns repeatedly, or comes with one-sided blockage, facial pain, nosebleeds or neurological symptoms. Persistent change may need assessment for sinus disease, COVID-19 or another cause, including Long COVID.

Does my blocked nose explain the smell change, or should I be assessed for sinus or allergic disease? Should I test for COVID-19? What should I do if smell does not return after my other symptoms improve?