For clinicians
When a patient reports smell loss.
Anosmia Awareness is a patient led nonprofit, not a clinical body. Clinicians keep arriving on this site, so here is the short version: what current guidance says about assessing olfactory loss, the tests available, the coding, and where to refer. Every clinical claim links to its source.
Why it gets missed, and why it matters
Smell loss is common and under-reported from both sides of the desk. A 2023 review in Deutsches Ärzteblatt International puts quantitative olfactory dysfunction at around 20 percent of the general population, anosmia near 5 percent and hyposmia near 15 percent. It also notes that subjective ratings are imprecise and often do not match measured olfactory capacity, and that patients judged recovered on self report frequently still test with residual deficits.
Source: Hummel, Liu, Müller, Stuck, Welge-Lüssen and Hähner, Deutsches Ärzteblatt International, 2023. Olfactory Dysfunction: Etiology, Diagnosis, and Treatment
COVID made the size of that gap visible. A meta-analysis led by the Monell Chemical Senses Center found smell loss in about 77 percent of COVID patients when smell was measured directly, and 44 percent when patients were asked.
Source: Monell Chemical Senses Center, reporting Hannum et al. in Chemical Senses. Better Measures Reveal More COVID-19 Smell Loss
The safety cost is measurable. Among 445 patients seen at a university smell and taste clinic, 37 percent of those with olfactory impairment reported at least one hazardous event, against 19 percent of those with normal olfaction. For patients with anosmia it was 45.2 percent. Cooking incidents accounted for 45 percent of the events, eating spoiled food or a toxic substance 25 percent, and undetected gas leaks 23 percent.
Source: Santos, Reiter, DiNardo and Costanzo, Archives of Otolaryngology Head and Neck Surgery, 2004. Hazardous Events Associated With Impaired Olfactory Function
The NIDCD notes that people with a smell disorder may eat too little and lose weight, or eat too much and gain it, and that severe cases can lead to depression. Patients rarely raise this on their own. It takes a direct question.
Source: NIDCD, National Institutes of Health. Smell Disorders
A workup that fits a normal appointment
History
The 2023 position paper in Rhinology is blunt: thorough clinical histories should be sought from all patients, agreed unanimously by its Delphi panel. The elements that change what you do next:
Onset and course. Sudden or gradual, complete or partial, stable or fluctuating.
Preceding illness. Upper respiratory infection, including COVID.
Head injury, including one from months earlier the patient no longer connects to it.
Nasal and sinus symptoms. Obstruction, discharge, facial pain, known polyps, and whether smell tracks with congestion.
Medications and exposures, plus smoking and prior radiation to the head and neck.
Neurological symptoms. Tremor, gait change, memory complaints, headache, new visual symptoms.
Distortion. Parosmia and phantosmia, which patients often will not mention unless asked.
Source: Whitcroft, Altundag, Balungwe and colleagues, Rhinology, 2023. Position paper on olfactory dysfunction: 2023
Examination
The same paper holds that patients with suspected olfactory dysfunction should undergo a full ENT examination including nasal endoscopy, with careful inspection of the olfactory cleft, at 98 percent panel agreement. Where endoscopy is not available in the room, that is part of what the referral is for.
Imaging
Imaging is chosen for a reason rather than ordered by default. The position paper recommends that structural imaging follow the suspected underlying aetiology. For idiopathic loss it makes CT of the paranasal sinuses optional and recommends MRI of the brain, at 91 percent panel agreement. The 2023 review describes MRI as the way to examine the olfactory bulb and the orbitofrontal cortex, and to establish whether an intracranial lesion such as an olfactory nerve meningioma is present.
Sources: Position paper on olfactory dysfunction: 2023 and Hummel et al., Deutsches Ärzteblatt International, 2023
Measuring smell rather than asking about it
Both guidance documents land in the same place. The international consensus statement on allergy and rhinology, published in 2022, states that olfactory function should be assessed by validated tests of odor threshold and either odor identification or discrimination. The 2023 position paper carries the same recommendation.
Source: Patel and colleagues, International Forum of Allergy and Rhinology, 2022. International consensus statement on allergy and rhinology: Olfaction
Sniffin’ Sticks covers threshold, discrimination and identification, with normative data from more than 9,000 subjects. The UPSIT is a 40 item, single use, self administered scratch and sniff test that grades severity against age and sex percentiles, with reported test retest reliability of 0.94. The same publisher supplies a 12 item Brief Smell Identification Test that runs to about five minutes.
Sources: Hummel et al., 2023, Sensonics International, Smell Identification Test (UPSIT) and Brief Smell Identification Test
A brief screen tells you whether to look further. Whichever you use, put the number in the chart. That is what makes the next visit comparable, and what a patient needs on paper if they later have to ask an employer or an insurer for something.
Coding it properly
The R43 family in ICD-10-CM covers disturbances of smell and taste. Each of these is billable.
R43.0 Anosmia.
R43.1 Parosmia.
R43.2 Parageusia.
R43.8 Other disturbances of smell and taste. This is where hyposmia sits. Indexed terms include sense of smell impaired and diminished sense of smell.
R43.9 Unspecified disturbances of smell and taste.
Source: ICD-10-CM 2026, R43 Disturbances of smell and taste
Specificity costs a second and pays off later. People write to us asking for documentation to support a workplace accommodation or a disability claim, and a specific coded diagnosis is what those requests get built on. Parosmia has its own code, and it is worth using.
Causes, in short
The NIDCD lists aging, sinus and upper respiratory infection, smoking, nasal polyps and other growths, head injury, hormonal problems, dental problems, chemical exposure, some medications, radiation to the head and neck, and conditions of the nervous system.
Source: NIDCD, National Institutes of Health. Smell Disorders
For a plain language version to hand a patient, our page on what anosmia is covers the categories and the vocabulary. Post viral loss has its own page on smell loss after COVID and parosmia, with the recovery timelines patients ask about.
What the evidence supports
Treat what is treatable
The 2023 position paper recommends systemic corticosteroids in short courses, or intranasal corticosteroids long term, for olfactory dysfunction secondary to chronic rhinosinusitis, severe allergic rhinitis and other inflammatory conditions, following existing guidelines for those diseases. Outside that group it finds limited evidence for corticosteroids, and where a topical steroid is used it favors a rinse over a spray so the drug reaches the olfactory cleft.
Smell training
Olfactory training has more evidence behind it than anything else available for acquired loss. A 2017 meta-analysis pooled 13 studies and found a significant positive effect on odor identification, odor discrimination and overall olfactory score, with longer training outperforming shorter. The 2023 position paper recommends it for post traumatic and post infectious loss at 98 percent panel agreement. The 2023 review sets the protocol at four odors, 20 to 30 seconds each, twice daily, for four to six months or longer. The original 2009 trial used 10 second exposures, and longer exposures are now generally recommended.
Sources: Sorokowska, Drechsler, Karwowski and Hummel, Rhinology, 2017, Effects of olfactory training: a meta-analysis, plus the 2023 position paper and Hummel et al., 2023
It is cheap and low risk, and it does not work for everyone. Saying that second part at the start saves the patient a bad afternoon three months in. Our smell training page has the method and where to get a kit.
Honest limits
No drug currently has solid evidence behind it for post infectious or post traumatic loss. The 2023 position paper finds insufficient clinical evidence for phosphodiesterase inhibitors and for calcium buffers in either. Patients often arrive having already spent money on supplements and sprays marketed for smell loss.
The neurological association, stated plainly
Olfactory loss is an established early feature of Parkinson disease. The 2023 review reports olfactory dysfunction in over 90 percent of people with idiopathic Parkinson disease, and notes it can appear more than 10 years before motor symptoms. Difficulty identifying odors also predicts conversion to dementia, at a reported conversion rate of 47 percent and an odds ratio of 5.1. The NIDCD puts the same point to patients in a line: a smell disorder can be an early sign of Parkinson disease, Alzheimer disease or multiple sclerosis.
Sources: Hummel et al., Deutsches Ärzteblatt International, 2023 and NIDCD, Smell Disorders
The direction of that association is what patients get wrong. Most people with Parkinson disease have smell loss. Most people with smell loss do not have Parkinson disease, and with olfactory dysfunction at roughly a fifth of the population, a poor smell test result is not a screening result for neurodegeneration. People who have read about the link online often arrive frightened. Take the history seriously, note any new neurological symptom, and go carefully before handing anyone a prognosis.
When to refer, and where
The NIDCD names the otolaryngologist as the specialist for smell and taste problems. Referral earns its place when the cause is not apparent, when there is nasal obstruction or suspected inflammatory disease, after head injury, or when the patient wants a measured baseline you cannot produce in clinic.
Source: NIDCD, National Institutes of Health. Smell Disorders
A smaller group needs a dedicated smell and taste center. Our resources page lists research and clinical centers in the United States, the United Kingdom and elsewhere, including Monell, the University of Pennsylvania and the Smell and Taste Clinic at Technische Universität Dresden. Several run studies, which is often what a motivated patient is really asking about.
For the patient in front of you
What patients tell us they needed to hear.
Validate it. What we hear most is that someone was told it was not serious. It is a sensory loss with the consequences for safety, eating and mood documented above, and hearing that acknowledged changes how people cope.
Cover home safety. Working smoke alarms and a natural gas detector matter more than usual. Advise patients not to rely on the sniff test for food. Dates are a starting point; time and temperature rules matter more: refrigerate promptly, date-mark leftovers, discard anything borderline.
Give them the protocol in writing. Our smell training page has the method, the schedule and where to buy a kit. It is free and meant to be handed out.
Point them at other people. The Story Wall collects first person accounts. Isolation is the part of smell loss a clinic cannot treat and other patients can.
This page is an educational summary from a patient led nonprofit. It is not a clinical guideline and not a substitute for your own judgment or for the primary sources linked above. Anosmia Awareness does not diagnose, treat or recommend treatment. Where guidance is cited here, please read the original.
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