Gargling to wash the throat is commonly performed in Japan, and people believe that
such hygienic routine, especially with gargle medicine, prevents upper respiratory
tract infections (URTIs). Its effectiveness, however, has not been established by
Randomized controlled trial carried out in 2002–2003 winter season and analyzed in
2003 and 2004.
Healthy volunteers (387) aged 18 to 65 years.
Participants were randomly assigned to water gargling, povidone-iodine gargling, and
usual care (control). Subjects in the two gargling groups were requested to gargle
with water or diluted povidone-iodine at least three times a day. Participants were
followed for 60 days.
Main Outcome Measures
The primary outcome measure was first URTI incidence. Severity of URTI symptoms among
incident cases was also evaluated. Both outcomes were assessed with a self-administered
symptom record. Analyses were performed on an intention-to-treat basis.
A total of 130 participants contracted URTIs. The incidence rate of first URTI was
0.26 episodes/30 person-days among control subjects. The rate decreased to 0.17 episodes/30
person-days in the water gargling group, and 0.24 episodes/30 person-days in the povidone-iodine
gargling group. Respective incidence rate ratios against controls were 0.64 (95% confidence
interval [CI]=0.41–0.99) and 0.89 (95% CI=0.60–1.33). A Cox regression (proportional
hazard model) revealed the efficacy of water gargling (hazard ratio=0.60, 95% CI=0.39–0.95).
Even when a URTI occurred, water gargling tended to attenuate bronchial symptoms (p=0.055).
Simple water gargling was effective to prevent URTIs among healthy people. This virtually
cost-free modality would appreciably benefit the general population.