Anosmia and dysgeusia: smell and taste loss — AU general practice approach

Smell loss is one of the most underrecognised sensory disabilities in Australian general practice. Before COVID-19, anosmia was considered a niche ENT presentation; since 2020 it has become one of the most commonly encountered post-viral sequelae, affecting hundreds of thousands of Australians. What makes it clinically complex is the diagnostic breadth — the same symptom can indicate anything from a recovering nasal polyp to the earliest prodrome of Parkinson’s disease — and the profound impact on quality of life, safety, and nutrition that goes largely unaddressed in brief consultations.

The terminology matters. Anosmia means total absence of smell; hyposmia means reduced smell; parosmia means real odours are perceived as distorted (usually foul — coffee, garlic, and onion classically smell like something rotting or chemical); phantosmia means phantom odours without any external stimulus. On the taste side, ageusia is total taste loss, hypogeusia is reduced, and dysgeusia is distorted taste. Crucially, about 80% of what we experience as “taste” is retronasal olfaction — the aroma of food reaching the olfactory epithelium from the back of the mouth. Most patients who report losing their sense of taste have actually lost their sense of smell. A simple clinical test: occlude the nose while tasting sweet versus sour; if they can distinguish the basic tastes, their true gustatory pathway is intact.

A. Core clinical — the AU general-practice framework

History

The highest-yield history questions are:

• Onset and trigger: sudden (post-viral, post-traumatic) versus insidious (rhinosinusitis, neurodegenerative)
• Timeline: did it follow a COVID-19 or other respiratory infection? Head injury even years ago?
• Laterality: bilateral (reassuring — most post-viral) versus unilateral (concerning — neoplasm until proved otherwise)
• Quality: complete loss, reduced, or distorted/parosmia? Ask about the “rotting smell” phase
• Prior episodes: intermittent suggests sinonasal disease with fluctuating mucosal oedema
• Medications: intranasal zinc gluconate (any branding — Zicam, homoeopathic “cold remedies”), ACE inhibitors (captopril causes dysgeusia), metformin, metronidazole, terbinafine, chemotherapy agents
• Neurological symptoms: tremor, slowness, micrographia, REM sleep behaviour disorder, memory change — the PD prodrome cluster
• Autoimmune screen triggers: dry eyes, dry mouth, joint pain, saddle nose, crusting, haemoptysis
• Functional impact: appetite, weight, depression, social withdrawal; at-risk patients (cooking for others, working with gas equipment)

Examination

Anterior rhinoscopy looking for nasal polyps (pale, glistening, insensate to touch), mucopus, septal deviation, or perforation. Cranial nerve I testing at the bedside: occlude one nostril; present coffee or vanilla from a non-aromatic carrier (avoid ammonia or menthol which activate trigeminal CN V and confound the result). Test each side separately.

In any patient with neurological concern, include a full screen: tremor, bradykinesia, cogwheel rigidity, MoCA cognitive score, visual fields by confrontation (pituitary macroadenoma compressing the olfactory tract also compresses the optic chiasm).

Oral examination for dysgeusia: smooth atrophic tongue (B12 or iron deficiency), coated tongue (oral candidiasis), dental hygiene, denture fit, dry mucosa (Sjögren syndrome).

Workup

Clinical diagnosis is primary in most cases. Target investigations to the clinical bucket:

• Allergy: skin prick or specific-IgE if allergic rhinitis is the suspected driver (ASCIA)
• Nutritional and endocrine: TSH, B12/folate, serum zinc, ferritin, HbA1c, vitamin D
• Autoimmune: ANA, ANCA, ENA, Ro/La (Sjögren), ESR/CRP — only when the clinical picture suggests a systemic cause
• CT sinuses (MBS 56013 range): for suspected structural/sinonasal cause, nasal polyps, suspected neoplasm, or pre-surgical assessment
• MRI brain with thin coronal cribriform cuts (MBS 63551 range): for unilateral anosmia, post-traumatic evaluation, or neurological features suggesting intracranial pathology — GP-referrable MRI items are available for specific indications; specialist referral may be required to access full rebatable protocols
• Psychophysical olfactory testing (UPSIT or Sniffin’ Sticks): objective quantification — not routinely MBS-rebated; specialist or research setting; particularly useful where medico-legal documentation is needed

B. Post-viral and post-COVID olfactory dysfunction

Post-viral anosmia is now the most common cause seen in Australian general practice. COVID-19 caused olfactory disturbance in approximately 30–50% of acute infections; at 12 months, around 1–5% still had significant impairment (Boscolo-Rizzo JAMA Otolaryngol 2022). Omicron variants appear to cause lower rates than ancestral or Delta strains.

The SARS-CoV-2 mechanism differs from other post-viral anosmia. The virus infects ACE2-expressing sustentacular support cells rather than olfactory neurons themselves, causing epithelial inflammation with secondary neuronal damage. Most cases resolve as the inflammatory response clears, but persistent loss reflects altered basal stem cell activity and neural circuit reorganisation.

Other respiratory viruses — rhinovirus, parainfluenza, influenza, RSV — cause classic post-viral sensorineural anosmia through direct olfactory mucosal damage.

Management:

1. Olfactory training is the most evidence-supported intervention across all post-viral aetiologies. The original Hummel Laryngoscope 2009 RCT demonstrated that the rate of recovery doubled versus controls. The Sorokowska Rhinology 2017 meta-analysis confirmed benefit across post-viral, post-traumatic, and idiopathic anosmia. Protocol: four odorants (rose, lemon, clove, eucalyptus) sniffed for 10 seconds each, twice daily, for at least 12 weeks, with the odorant set rotated every 12 weeks. AbScent provides free training kits. The biological rationale is olfactory neuron regeneration from basal stem cells — repetitive stimulation drives this process.

2. Intranasal corticosteroid (mometasone 50 µg two sprays per nostril daily, fluticasone propionate 50 µg two sprays daily) adds modest benefit, particularly where any sinonasal component is present. The Hura IFAR 2020 evidence-based review found modest benefit when combined with olfactory training.

3. Systemic corticosteroids are not recommended for isolated post-viral anosmia — the Hura review found limited net benefit and significant systemic risk. Reserve oral prednisolone for CRSwNP exacerbations only.

4. Omega-3 supplementation: a single small trial (Yan IFAR 2020) suggested modest benefit post-COVID; considered an optional adjunct, not standard of care.

C. Chronic rhinosinusitis with nasal polyps and other sinonasal causes

Chronic rhinosinusitis with nasal polyps (CRSwNP) has a prevalence of approximately 2–4% in Australian adults and causes hyposmia in 70–90% of cases (EPOS 2020). The loss is conductive — physical obstruction of odorant access to the olfactory cleft — and is therefore potentially fully reversible with adequate treatment.

Treatment hierarchy per EPOS 2020 and AMH:

• Intranasal corticosteroid (first-line; PBS General Schedule for allergic rhinitis)
• High-volume saline nasal irrigation twice daily
• Short oral prednisolone course (25–50 mg daily for 5–14 days) for severe exacerbations — limit to 1–2 courses per year
• Dupilumab (Dupixent, anti-IL-4Rα): PBS Authority Required for severe CRSwNP ≥18 years on stable maximal medical therapy, specialist-initiated. The SINUS-24/52 Lancet 2019 trials demonstrated significant improvement in olfaction scores alongside polyp reduction
• ENT referral for functional endoscopic sinus surgery (FESS) in refractory cases

Allergic rhinitis as a cause of mild intermittent anosmia responds to intranasal corticosteroid and antihistamines per ASCIA guidelines. Seasonal pattern, associated itching, sneezing, and atopic history are the discriminators.

D. Australian operations

MBS billing for anosmia workup in general practice:

• Standard consultations: item 23, 36, 44
• Telehealth where existing-relationship rule met: video 91790, phone 91891 — most anosmia review consultations are telehealth-suitable unless formal rhinoscopy is needed
• GP Chronic Condition Management Plan 965/967 — chronic post-COVID or CRSwNP anosmia qualifies; allows up to five allied-health sessions per year
• Dietitian 10954 (parosmia-related weight loss and food strategies)
• Psychology 10968 (adjustment disorder, depression secondary to anosmia)
• Mental Health Care Plan 2715/2717: chronic anosmia is associated with a 30% rate of depressive symptoms — low threshold for a plan
• FBC 65070; B12/folate 66602; TSH 66719; specific IgE 71161

PBS prescribing: intranasal corticosteroids are PBS General Schedule for allergic rhinitis (mometasone, fluticasone propionate, budesonide, beclomethasone); dupilumab is Authority Required for severe CRSwNP.

TGA flag: intranasal zinc gluconate products remain contraindicated since 2009 — includes all homoeopathic zinc nasal preparations regardless of branding. Oral zinc is unaffected.

Medico-legal: post-traumatic anosmia is frequently a medico-legal matter — document objective testing (UPSIT or Sniffin’ Sticks via ENT referral) rather than subjective report alone.

E. Special populations

Older adults (≥50 years): New anosmia in someone over 50 with any motor or cognitive feature warrants neurology referral for Parkinson’s disease workup. Olfactory dysfunction precedes motor symptoms by 4–7 years (Doty Nat Rev Neurol 2012) and is also an early Alzheimer’s biomarker. Annual cognitive and motor screening is appropriate for any older adult with persistent unexplained isolated anosmia.

Pregnancy: Avoid intranasal corticosteroid in the first trimester without specialist input. Olfactory training carries no risk and is appropriate. Dysgeusia in pregnancy is common and usually resolves postpartum — but screen for nutritional deficiencies (zinc, iron, B12).

Aboriginal and Torres Strait Islander patients: CRSwNP and allergic rhinitis are more prevalent. The ATSI Health Assessment MBS 715 provides a structured review opportunity.

Kallmann syndrome (congenital anosmia + hypogonadotrophic hypogonadism, often with cleft lip/palate): should be on the differential in any young person presenting with lifelong anosmia and delayed puberty — refer to endocrinology and clinical genetics.

When to escalate

Refer or escalate when:

• Same-week ENT: unilateral persistent anosmia; blood-tinged unilateral nasal discharge; facial numbness; suspected sinonasal neoplasm; post-COVID anosmia failing to improve at 6 months on olfactory training + intranasal corticosteroid; CRSwNP refractory to 8 weeks of intranasal corticosteroid + irrigation
• Urgently to ED + ENT: sudden bilateral anosmia with headache/focal neurology/altered consciousness; CSF rhinorrhoea post-trauma; suspected invasive fungal sinusitis in immunocompromised patients
• Neurology: age >50 with new anosmia and any motor or cognitive signs; isolated persistent anosmia at annual surveillance if motor/cognitive features emerge
• Endocrinology + genetics: suspected Kallmann syndrome (anosmia + delayed puberty + hypogonadism)

What this article is and is not

This is general health information drawn from current Australian general practice guidelines — RACGP AJGP, AMH, EPOS 2020, ASCIA, ASOHNS, and major olfactory training trials. It is not personal medical advice and does not create a doctor–patient relationship. Decisions about investigation and treatment are made with your own GP and treating clinicians.

For Australian patient resources: Better Health Channel — Smell and taste, HealthDirect — Anosmia, AbScent.

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Sources cited

1. RACGP AJGP — Smell and taste disorders after COVID-19 (2022)
2. ASCIA — Allergic rhinitis clinical update
3. ASOHNS — Australian Society of Otolaryngology Head and Neck Surgery
4. AMH — Australian Medicines Handbook
5. TGA Safety Alert — intranasal zinc gluconate (2009)
6. EPOS 2020 — Fokkens et al. Rhinology 2020
7. Hura N et al. Treatment of post-viral olfactory dysfunction. Int Forum Allergy Rhinol 2020
8. Hummel T et al. Effects of olfactory training. Laryngoscope 2009;119:496–9
9. Sorokowska A et al. Olfactory training meta-analysis. Rhinology 2017;55:17–26
10. Boscolo-Rizzo P et al. Sequelae at 12 months after COVID-19. JAMA Otolaryngol 2022;148:889–91
11. Doty RL. Olfactory dysfunction in Parkinson’s disease. Nat Rev Neurol 2012;8:329–39
12. Davidson TM, Smith WM. Zinc-induced anosmia: causality analysis. Arch Otolaryngol 2010;136:673–6
13. Better Health Channel — Smell and taste
14. HealthDirect — Loss of smell
15. AbScent