Acute upper respiratory tract infections (URTIs) include the common cold, inflammation of the trachea and larynx with symptoms including fever, cough, pain and headaches. Most acute URTIs are caused by viral infections and usually resolve after three to seven days. To reduce the course of the infection and make the person feel more comfortable, paracetamol, ibuprofen or aspirin and maintaining fluid intake are often recommended to reduce fever and ease pain and headaches. Antibiotics are prescribed if the illness becomes chronic and complications develop. Some live micro-organisms can confer a health benefit to the patient when administered in adequate amounts. Lactic acid bacteria and bifidobacteria are the most common types of probiotics. They are commonly consumed in fermented foods, such as yogurt and soy yogurt, or as dietary supplements.
We searched electronic databases and identified 14 randomised controlled trials, although we could only extract available data to pool from 10 trials which involved 3451 participants, including infants, children and adults aged around 40 years. The live micro-organisms intervention was found to be better than placebo in reducing the number of participants experiencing episodes of acute URTI and the rate ratio (calculated to compare the rate of events occurring at any given point in time) of episodes of acute URTI but the results in our review showed some limitations (for example, a high level of heterogeneity, few studies in some subgroups and no data for older people). Limited information from only three of the trials showed that live micro-organisms can reduce the prescription of antibiotics. Side effects of probiotics were minor and gastrointestinal symptoms were the most common.
The evidence is weak but our review shows a benefit in using probiotics to prevent acute URTIs.