What is the treatment for parosmia?

Treatment for Parosmia

Olfactory training is the most effective first-line treatment for parosmia, particularly using the modified olfactory training (MOT) protocol which has shown effectiveness for COVID-19-induced parosmia. 1

Understanding Parosmia

Parosmia is a qualitative olfactory disorder characterized by distorted smell perception, where familiar odors become altered and often unpleasant. It has gained significant attention during the COVID-19 pandemic as a common post-infectious symptom.

Key characteristics:

• Typically occurs as a delayed symptom after virus-induced anosmia 2
• Often triggered by specific substances, particularly thiols and pyrazines 1, 3
• Can significantly impact quality of life, mental well-being, and dietary habits 1
• May persist for extended periods, with some cases lasting 5-10 years 4

Diagnostic Approach

When evaluating a patient with parosmia:

1. Determine the likely etiology:

   • Post-viral (especially COVID-19)
   • Sinonasal diseases
   • Traumatic brain injury
   • Neurological conditions
   • Medication-induced
   • Toxic chemical exposure 1

2. Distinguish from phantosmia:

   • Parosmia: distorted perception of actual odors
   • Phantosmia: perception of odors in the absence of stimuli 1

Treatment Algorithm

First-line Treatment:

1. Modified Olfactory Training (MOT):
   • Systematic exposure to specific odors to retrain the olfactory system
   • Shown to be effective specifically for COVID-19-induced parosmia 1
   • Protocol typically involves daily exposure to selected scents for several months

Second-line Options:

1. Supportive Measures:

   • Patient education about trigger avoidance
   • Dietary modifications to avoid triggering foods
   • Psychological support for associated distress

2. Experimental Approaches:

   • Hyperbaric oxygen therapy has shown promise in case reports for COVID-19-related parosmia 5

Important Considerations:

• Avoid oral steroids in COVID-19-related cases due to potential risk of increased viral shedding 2
• Recovery is often gradual and may take months to years
• Unlike other post-COVID symptoms that may worsen over time, parosmia typically improves gradually 2

Molecular Understanding and Prognosis

Recent research has identified specific molecular triggers for parosmia, suggesting it may be partly a receptor-level phenomenon rather than solely a central processing issue 3. These trigger molecules:

• Share characteristics such as extremely low olfactory thresholds
• Have common molecular structures
• Are frequently found in foods reported as problematic by parosmia patients

Prognosis

• Most cases of parosmia improve over time, particularly post-viral cases
• In the general population, approximately 4.8% report parosmia experiences
• For some individuals, parosmia can persist for 5 years (17%) or even 10 years (10.3%) 4
• COVID-19-related parosmia typically has onset around 3 months after initial infection 2

Pitfalls to Avoid

1. Misdiagnosis: Don't confuse parosmia with phantosmia, as management approaches differ
2. Underestimating impact: Parosmia can significantly affect nutrition and mental health
3. Promising quick recovery: Set realistic expectations about the potentially prolonged course
4. Overuse of steroids: Avoid systemic steroids in COVID-19-related cases unless clear benefit is established

By implementing olfactory training early and providing appropriate supportive care, many patients with parosmia can experience gradual improvement in their symptoms and quality of life.