Loss of Smell After COVID-19: New Research Highlights Lingering Effects

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A new study reveals that loss of smell—known medically as hyposmia—can persist for years after COVID-19 infection, affecting both those who noticed symptoms and many who did not realize their sense of smell was compromised.

Key Findings

Researchers from the US National Institutes of Health and New York University Langone Health conducted an objective study, using a 40-odour test, to assess smelling ability after COVID-19. The study involved 3,535 men and women, making it the largest to formally evaluate post-COVID smell loss using clinical testing.

80% of participants who reported changes in their sense of smell after COVID-19 earned low scores on a clinical scent-detection test taken about two years post-infection.
Within this group, 23% were severely impaired or had entirely lost their sense of smell.
Remarkably, 66% of infected participants who reported no issues with their sense of smell also scored abnormally low, indicating “silent” hyposmia.
For comparison, 60% of uninfected participants who did not report olfactory issues also performed poorly but at lower rates than those post-COVID.

Expert Perspectives

Dr. Leora Horwitz, co-lead author and professor at NYU Grossman School of Medicine, emphasized, “Our findings confirm that those with a history of Covid-19 may be especially at risk for a weakened sense of smell, an issue that is already underrecognized among the general population”.

Independent experts not involved in the research note that olfactory dysfunction can impact daily life beyond merely sensing odors—it may affect appetite, safety, and even mental health. Dr. James Schwob, professor of otolaryngology at Tufts University (quote sourced from similar studies), explains, “The sense of smell is fundamental for flavor perception and warning against hazards like smoke or gas leaks. We must pay closer attention to post-viral changes in this sensory system”.

Background and Context

Anosmia (total loss of smell) and hyposmia have been widely reported since the early months of the pandemic, appearing in up to half of COVID-19 cases at the peak. Previous studies showed many people eventually regained their sense of smell, but increasing evidence suggests a subset of patients experience long-term or even permanent olfactory deficits.

The reason for lingering loss of smell is not fully understood. Experts suspect damage to specialized nerve cells in the nose and inflammation caused by the virus may disrupt the neural signaling needed for scent perception.

Public Health Implications

The study’s findings suggest healthcare providers should routinely evaluate smell loss in patients who have had COVID-19, including those who do not report symptoms. Routine olfactory testing may help identify cases of silent hyposmia and enable early intervention and support.

Potential therapies include:

Olfactory training: Systematic exposure to strong scents to help “rewire” the neural response.
Vitamin A supplementation: Early research is exploring whether this nutrient supports nerve cell recovery.
These interventions are still being evaluated, and more robust clinical trials are needed.

Practical Implications for Readers

Loss of smell can impact safety—for example, missing warning odors—and quality of life, affecting the enjoyment of food and daily pleasures. Readers are encouraged to be mindful of changes in their sense of smell and report them to healthcare providers, especially after respiratory infections.

Individuals who experienced COVID-19, whether or not they noticed changes, may benefit from requesting a clinical assessment of their olfactory function.

Limitations and Counterarguments

The study focused largely on self-reported infection history and a U.S.-based sample, which may limit global generalizability. Not all participants had laboratory-confirmed COVID-19, and there may be other factors—such as age, pre-existing conditions, or environmental exposures—that influence loss of smell.

Importantly, abnormal test scores were also found in a significant proportion of uninfected individuals, suggesting broader factors at play. More research is needed to separate COVID-specific impacts from general olfactory health issues.

Conclusion

Loss of smell after COVID-19 is more common and longer-lasting than previously recognized, affecting daily life and well-being. With ongoing research and emerging therapies, there is hope for improved detection and management of post-COVID olfactory dysfunction.

Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.