Changes in the ability to smell are a common symptom of COVID-19. Studies suggest that up to 85% of individuals infected with SARS-CoV-2 experience some degree of olfactory dysfunction, with a subset enduring these issues for months, or even years, after their initial recovery. Especially patients affected by Long COVID experience olfactory dysfunction besides other symptoms.
Symptoms include both loss of smell (anosmia) or smell distortion (parosmia). These persistent sensory issues significantly affect quality of life, making effective treatment methods a priority for both researchers and clinicians.
In this blog post, we briefly discuss how COVID-19 can lead to olfactory disorders. We also present the potential benefits of saline and corticosteroid nasal sprays for preventing and treating olfactory disorders.
In a second blog, we summarize the results of four studies that investigate various pharmacological interventions for their potential to benefit people with olfactory disorders.
Understanding the Mechanisms Behind COVID-19 Induced Olfactory Dysfunction
COVID-19-induced olfactory dysfunction is thought to result from the virus's interaction with olfactory receptor neurons (ORNs) located in the nasal cavity. These neurons play a key role in detecting odors and forwarding information to the brain. The SARS-CoV-2 virus is believed to cause damage to these neurons, either directly or through inflammation, leading to the loss or alteration of smell.
While many patients regain their olfactory function in the weeks following their illness, others suffer from prolonged or permanent loss.
Currently several different treatment strategies for olfactory dysfunction following COVID-19 are under investigation.
Current Treatments and Emerging Therapies
As mentioned previously in our literature overview, several studies assessing treatment options have been published this year. Here, we give an overview on the results of a selection of clinical trials on olfactory dysfunction following COVID-19.
- Early Use of Saline Nasal Irrigation and Corticosteroid Nasal Spray
A recent double-blind randomized controlled trial investigated the early use of saline nasal irrigation (SNI), corticosteroid nasal spray, and mouthwash in preventing olfactory and gustatory dysfunctions (OGDs) in COVID-19 patients.
The trial enrolled 379 patients. All patients included have been admitted to hospitals due to COVID-19 without showing any signs of OGDs at admission. Participants were randomized into three groups: a control group, a saline group, and a corticosteroid group.
The study found that the incidence of OGDs was significantly lower in both the saline (11.8%) and corticosteroid (8.3%) groups compared to the control group (40%). Furthermore, both interventions not only reduced the prevalence but also lessened the severity of OGDs.
These findings underscore the potential of early interventions in preventing COVID-19-related sensory dysfunctions. The results are especially interesting due to the larger sample size. Offering saline or corticosteroid nasal spray to people during their acute SARS-CoV-2 infection could decrease the occurrence of long-term olfactory dysfunction. Moreover, this could reduce the neurological complications associated with OGDs.
- Olfactory Training with Topical Nasal Corticosteroids
A study examined the combined effect of olfactory training (OT) and topical nasal corticosteroids in patients with olfactory dysfunction post-COVID. Twenty patients were randomized into two groups: OT alone and OT combined with topical nasal corticosteroids (mometasone furoate nasal spray).
After three months, both groups showed improvement in olfactory function, but the group receiving topical nasal corticosteroids exhibited more sustained recovery.
The study concluded that while olfactory training alone may offer quicker short-term benefits, combining it with topical nasal corticosteroids provides longer-lasting improvement in olfactory function.
If you are experiencing changes in smell and taste yourself, check out our guidebook on olfactory training or discuss your experiences in the Altea Forum.
