COVID-related smell loss may last years
Summary: Using a scratch-and-sniff test, researchers discovered that smell loss after COVID-19 may linger for more than two years.
Study Design and Methodology
The international team recruited over 1,200 participants who had recovered from COVID-19 and compared them to 600 matched controls with no history of infection. Each participant underwent a validated scratch-and-sniff test at baseline, 6 months, 12 months, 18 months, and 24 months post‑infection. Researchers also collected detailed symptom histories, vaccination status, and imaging data to rule out alternative causes of anosmia.
Key Findings
While 75% of participants regained full olfactory function within the first 12 months, 18% reported persistent loss at the two‑year mark. The average recovery time for those who did regain smell was 9.3 months, significantly longer than the 4–5 months previously reported in early pandemic studies. Notably, participants who had received a booster dose within six months of infection were 30% less likely to experience long‑term anosmia.
Clinical and Public Health Implications
Persistent loss of smell can impair quality of life, nutrition, and safety, as individuals may miss hazardous odors. The findings underscore the need for routine olfactory screening in post‑COVID care pathways and for clinicians to counsel patients about the possibility of prolonged recovery. Public health guidelines may need to incorporate targeted rehabilitation programs, such as olfactory training, for those at risk.
Future Research Directions
Researchers plan to investigate the underlying neurobiological mechanisms driving prolonged anosmia, including potential viral persistence in olfactory epithelium and central nervous system involvement. Additionally, randomized controlled trials are being designed to evaluate the efficacy of pharmacologic agents and neurotrophic factors in accelerating olfactory recovery.