Anosmia, a loss of sense of smell (and associated taste), is most commonly associated with:
- COVID 19 (and can persist as a feature of long Covid)
- Following rhinovirus or influenza virus infection
- Natural ageing
- Following head trauma
- Rarely orbito-frontal conditions, which may involve the optic nerve too.
The Covid virus appears to target nerve endings in the olfactory epithelium and olfactory bulb. Unlike the common cold, the nose is often not blocked, and anosmia can be profound. Dysosmia (distorted perception of smell) may also be a feature. Referral is not indicated unless there are other complications: the indications are that the vast majority improve in the first 2-3 weeks, and 90% recovered substantially or completely by 6 weeks.
In non-COVID viral infections loss of smell is common in association with nasal obstruction but a small minority of patients suffer from persistent anosmia or hyposmia. The evidence is that the majority of those with symptoms at two months will recover: a third within 6 months and two thirds at eighteen months.
Useful patient leaflets on anosmia:
- Loss of sense of smell
- Smell disorders – managing your recovery (after a virus)
A small number of people have permanent loss of smell and taste, but please see Primary Care Management and Resources and Links for approaches which will hopefully help.
Referral is not indicated unless there are other symptoms of concern.
‘Smell training’ which stimulates the damaged nerve endings seems to improve both threshold (ability to smell) and discrimination. Stopping smoking is also helpful. Explanation and support are crucial: for some this can be a very distressing condition, often underestimated by others.
Two helpful charities are Fifth Sense (https://www.fifthsense.org.uk/) and AbScent (https://abscent.org/).
