Over-the-Counter Probiotics Can Lower Acute Upper Respiratory Tract Infection Risk

OCTOBER 01, 2013
Frank J. Domino, MD

Frank J. Domino, MD


Hao Q, Lu Z, Dong BR, Huang CQ, Wu T. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Syst Rev. 2011 Sep 7;(9):CD006895. http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD006895.pub2/abstract.

Study Methods

This was a systematic review of 14 randomized controlled trials involving 3,451 patients with acute upper respiratory tract infections (URTIs).

Patient Demographics

Though the trials were diverse in population, they may have contained greater representations of patients from Asian cultures, where the use of probiotics may have more societal acceptance.

Intervention and Control

Probiotic strains were compared to placebo on outcomes that included URTI development, length of illness, and adverse events. Commonly used strains in this study comprised of Lactobacillus acidophilus, L. casei, L. gasseri, L. bulgaricus, L plantarum, L. paracasei, L. rhamnosus, Streptococcus thermophiles, and Bifidobacterium lactis.

Results and Outcomes

Probiotics were superior to placebo in participants who experienced episodes of acute URTI. The odds ratio (OR) to prevent at least 1 URIT was 0.58 [95% confidence interval (CI) 0.36 to 0.92], while the OR to prevent at least 3 episodes was 0.53 (95% CI 0.36 to 0.80). In addition, the reduction in acute URTI episodes from probiotic strains lowered antibiotic prescription rates (OR 0.67; 95% CI 0.45 to 0.98).
However, probiotics didn't alter the mean duration (MD) of an episode of acute URTI versus placebo (MD -0.29; 95% CI -3.71 to 3.13), and the odds of an adverse event occurring didn't differ between the intervention and placebo groups (OR 0.92; 95% CI 0.37 to 2.28). 

Side effects of probiotics were minor, with gastrointestinal (GI) symptoms being the most common.


When taken daily, an over-the-counter (OTC) probiotic — typically of a Lactobacillus strain — lowered the risk of URTIs in the general population without increasing the risk of adverse events.

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