The easy three-times-a-day habit to cut infection risk by 36% — but there’s a catch

A Japanese habit known as “ugai”, or rinsing the mouth with water, may help prevent respiratory infections, but evidence is mixed. One study found fewer illnesses among people who gargled three times a day, while later research has not consistently reproduced that result.

In the 2005 study, 387 adults aged 18 to 65 were followed through a winter cold season: the plain-water group had a 36% lower illness incidence than those who did not gargle, while diluted povidone-iodine showed no statistically significant benefit. A 2014 study found no difference, and a review of the two studies concluded there was little to no evidence that water gargling prevents infections. Gargling may still ease symptoms once someone is ill; studies cited in the article found saltwater gargling with nasal rinses shortened colds by two days, and medicated mouthwash helped throat pain.