Smell Diminishes by Day 3 of COVID-19, Study Says

Sense of smell most often diminishes by the third day of infection with the new coronavirus, and many patients also lose their sense of taste at the same time, a new study finds.

The findings may help identify patients most likely to benefit from antiviral treatment, according to the researchers.

“The relationship between decreased sense of smell and the rest of the COVID-19 is something to be aware of. If someone has a decreased sense of smell with COVID-19, we know they are within the first week of the disease course and there is still another week or two to expect,” said principal investigator Dr. Ahmad Sedaghat of the University of Cincinnati College of Medicine.

His team examined characteristics and symptoms of 103 patients in Switzerland who were diagnosed with COVID-19 over six weeks. The patients were asked how many days they had COVID-19 symptoms and also about the timing and severity of lost or reduced sense of smell, along with other symptoms.

At least 61% of the patients reported reduced or lost sense of smell, and the average onset for this was 3.4 days, according to the study. The findings were published online recently in the journal Otolaryngology-Head and Neck Surgery.

Problems with sense of smell were more likely to occur in younger patients and women.

“We also found in this study that the severity of the loss of smell is correlated with how bad your other COVID-19 symptoms will be,” Sedaghat said in a university news release. He’s an associate professor of otolaryngology-head and neck surgery.

“If the anosmia, also known as loss of smell, is worse, the patients reported worse shortness of breath and more severe fever and cough,” added Sedaghat.

He noted that an antiviral drug called remdesivir has shown some promise in treating COVID-19 patients.

“Antiviral medications have historically worked best when given early during a viral infection. The same is hypothesized to be true for remdesivir,” Sedaghat said. “Our study indicates that a decreased sense of smell may be an indicator of patients early in the disease course as well as those who may go on to develop more severe symptoms, like shortness of breath, later on.”

If “remdesivir becomes more widely available, decreased sense of smell may therefore identify patients who would be excellent candidates for the medication,” he said.

Another finding was that about half of the patients had a stuffy nose and 35% had a runny nose. This is important because previous research suggested that these symptoms were rare in COVID-19 patients, and that these symptoms were attributed to allergy and not the new coronavirus, according to Sedaghat.

“This just means that greater awareness is needed of COVID-19’s nasal symptoms so people are not running around sneezing in public and thinking it is OK since this is just allergies,” he said. “It very well could be COVID-19, and wearing masks as protective gear for others you encounter is a good idea.”

More information

The U.S. Centers for Disease Control and Prevention has more on COVID-19.