March 10, 2026
The spotlight on smell loss during the COVID-19 pandemic has shed new light on the underlying causes of anosmia, which is complete smell loss. Mayo Clinic physicians and researchers are expanding treatment options and working to understand how anosmia might correlate to other chronic diseases.
"With our growing knowledge about smell loss and the introduction of new and promising therapies, the field is evolving and the changes are exciting," says Osarenoma U. Olomu, M.D., an otolaryngologist at Mayo Clinic in Jacksonville, Florida.
Expanding the understanding of what causes anosmia
The long-standing belief within the medical community is that the primary cause of anosmia is damage to olfactory sensory neurons. The fine nerve fibers, which travel through bone to connect the olfactory bulb to the nasal epithelium, are vulnerable to trauma and viral infections. When olfactory neurons are affected by physical trauma, inflammation or viral infection, it can impair olfactory function.
However, the loss of smell experienced with SARS-CoV-2 infection broadened the understanding of hyposmia, also known aspartial smell loss, and anosmia. It revealed the essential role of sustentacular cells — the supporting cells that keep olfactory nerves healthy. SARS-CoV-2 infects sustentacular cells, not the neurons, and it can induce olfactory dysfunction, often as the initial symptom.
"Before COVID-19, we did not fully understand how critical sustentacular cells are to the maintenance and function of the olfactory nerves," Dr. Olomu says. "Researchers are now examining the effects of irritants and other structures and substances on these supporting cells."
Introducing novel anosmia treatments to improve outcomes
The primary care physician typically conducts first line treatment for anosmia, which may include:
- Olfactory training: Exposing the nose to different odorants to help the brain realign with smell fibers improves sense of smell in about 26% of people with anosmia.
- Nasal steroid irrigation: Using a steroid rinse in addition to olfactory training doubles the recovery rate, restoring smell for about 50% of patients.
"Data show that a combination of nasal irrigation and olfactory training is the best treatment approach we have right now for anosmia," Dr. Olomu says. "But the question has always remained, how do we treat the other 50% of patients who have not seen improvement in their sense of smell?"
The answer may be platelet-rich plasma (PRP) therapy. PRP contains anti-inflammatory and growth factors that may help damaged olfactory neurons recover.
A study published in International Forum of Allergy & Rhinology assessed long-term outcomes of PRP injections into the olfactory cleft. One year after the initial treatment, 87% of patients who received PRP therapy showed clinically significant improvement in their sense of smell.
"The most compelling part is that the study specifically looked at people who were past the window of spontaneous recovery and who already went through standard of care treatment with no success," Dr. Olomu says. "For patients who have essentially exhausted their treatment options, using PRP for anosmia offers the potential to regain their sense of smell."
PRP therapy is an advanced treatment option offered in only a few locations nationwide. Mayo Clinic in Florida has added PRP to its treatment protocol for anosmia.
Searching for a connection between anosmia and neurodegenerative disorders
Mayo Clinic physicians are working to define the connection between anosmia and neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease.
"Older adults who completely lose their sense of smell — especially if they are unaware they've lost it — have a nearly 100% chance of developing a severe neurodegenerative disorder within five years," Dr. Olomu says.
What experts don't know is which comes first. Is anosmia a marker that neurodegenerative disease is present? Or is the loss of smell contributing to the development of those disorders?
To learn more, Mayo Clinic researchers are reviewing the records of patients who permanently lost their sense of smell for any reason in their 30s and 40s. They are looking for any correlation with increased risk of neurodegenerative disorders later in life.
"Our goal is to see if losing your sense of smell predisposes you to developing dementia in the future," Dr. Olomu says.
Benefits of partnering with an otolaryngologist to treat anosmia
Referring patients to specialized care can provide access to advanced treatment and clinical trials. If patients have not recovered their sense of smell after six months of olfactory training and nasal steroid irrigation, specialized care should be the next step.
"If patients haven't recovered their smell by six months, they likely won't recover it by continuing treatment," Dr. Olomu says. "A specialist may be able to help, but the timing is critical. Referring patients at that six-month mark is well before olfactory function experiences permanent damage."
Otolaryngologists have extensive experience performing standard of care treatments and may expand the treatment protocol to include:
- Stronger nasal rinses.
- Tests for nutritional deficiencies and metabolic issues.
- Nasal endoscopy to check for a blockage.
"We are really excited for the advances being made in the treatment of anosmia," Dr. Olomu says. "Patients who aren't responding now have more options than they may realize."
For more information
Fieux M, et al. Long-term outcomes of PRP injections for post-viral olfactory loss: A prospective cohort study. International Forum of Allergy & Rhinology. 2025;15:420.
Refer a patient to Mayo Clinic.