NHS Tayside RefGuide
The perception of smell and taste and closely intertwined. Olfactory disorders can be classified as either a loss of ability to smell odours or a distortion of odours. Anosmia is complete lack of smell with hyposmia being a reduction and dysosmia referring to a distortion.
Smell disorders are very common in the general population with a prevalence of around 20%. The majority of these cases are related to the deterioration in function as a result of the aging process, this being similar to progressive hearing loss. Around 1% of the adult population under 65 have a major olfactory dysfunction.
The most common causes are:
- Upper respiratory tract infections
- Trauma
- Sinonasal pathology
- Medication
In primary care:
- Try to identify if there are any neurological symptoms or signs which may indicate a more central cause.
- In the elderly there is a link between smell disorders Alzheimer and Parkinsons, so look for signs of cognitive impairment.
- Identify any recent change in medication
- Rule out undiagnosed medical co-morbidity with bloods for renal function, liver function, thyroid disease and diabetes.
- Look for evidence of red flag symptoms (unilateral block or bloody discharge, bleeding, paraesthesia of the face, change in vision or ill fitting dentition).
If the above has been ruled out and especially if the patient has other nasal symptoms, a topical nasal steroid in terms of a spray or drops should be trialled.
There are significant psychological consequences of losing your sense of smell. There are excellent support groups and charities out there now for patients to access, they should be directed to the websites below.
Safety measures to tell patients include:
- Gas and smoke alarms to be on the mains rather than battery powered
- Care to be taken with food sell by dates.
Due to loss of smell and taste being so common in patients with COVID-19, it is important to follow local guidance regarding testing patients with an acute loss/change in their sense of smell.