Treatment Recommendations for Long-Term COVID-19 Related Anosmia
For patients with anosmia secondary to COVID-19 that has persisted for over 2 years, olfactory training should be recommended as the first-line treatment due to its safety profile and evidence of effectiveness, while other interventions should only be considered within clinical trials.
Understanding COVID-19 Related Anosmia
Post-viral olfactory loss (PVOL) from COVID-19 occurs through several mechanisms:
- Inflammation of olfactory clefts
- Damage to olfactory epithelium
- Involvement of ACE2 receptors on sustentacular cells
- Local inflammation rather than direct neural damage 1
While most COVID-19 related anosmia resolves spontaneously within weeks, approximately 10-20% of patients experience persistent symptoms beyond 6 months, with some cases lasting years.
Evidence-Based Treatment Approach
First-Line Treatment: Olfactory Training
- Recommended for all patients with persistent anosmia 2, 1
- Implementation protocol:
- Systematic exposure to 4 different strong odors (typically rose, eucalyptus, lemon, and clove)
- Practice twice daily for at least 12 weeks
- Sniff each odor for 10-20 seconds with focus and concentration 1
- Continue for at least 3 months, with potential benefit from longer training periods
Second-Line Treatments (Limited Evidence)
Intranasal corticosteroids:
- Evidence is insufficient to provide a firm recommendation for or against use 2
- Studies show conflicting results:
Intranasal insulin:
- Limited evidence from one small RCT showing significantly higher olfactory detection scores with intranasal insulin fast-dissolving film 2
- Not recommended as standard treatment due to insufficient evidence
Systemic corticosteroids:
- Very limited evidence from one small study (18 participants) using oral steroids combined with nasal irrigation 5
- The evidence regarding benefits and harms is very uncertain
- Not recommended outside clinical trials due to potential side effects and limited evidence
Special Considerations
Monitoring and Follow-up
- Assess olfactory function using validated tools when available
- Evaluate for development of parosmia (distorted smell), which may predict recovery of aspects of quantitative smell loss 6
- Consider referral to specialized smell and taste clinics for patients with severe or persistent symptoms beyond 6 months
Safety Concerns
Advise patients about safety issues related to anosmia:
- Install gas and smoke alarms
- Check food expiration dates carefully
- Be cautious with gas appliances 1
Quality of Life Impact
- Persistent anosmia significantly decreases quality of life and should be addressed proactively 1
- Patients with parosmia report increased anxiety and decreased quality of life 6
- Prepare patients for the possibility that symptoms may persist for years 6
Common Pitfalls to Avoid
- Assuming spontaneous recovery will occur - While common in the first few months, recovery becomes less likely after 6-12 months
- Overreliance on unproven therapies - Many proposed treatments lack sufficient evidence
- Dismissing the psychological impact - Anosmia significantly affects quality of life and mental health
- Inadequate duration of olfactory training - Training must be continued for at least 12 weeks to show benefit
Conclusion
The evidence for treating persistent COVID-19 related anosmia is limited. Olfactory training represents the safest and most evidence-supported intervention, while other pharmacological treatments should be considered experimental until more robust evidence emerges.