limited conclusions can be drawn. The trial relied on self reported episodes of the common cold but was of reasonable quality in terms
of randomisation and allocation concealment. Adverse effects included rash and odour.
Authors’ conclusions
There is insufficient clinical trial evidence regarding the effects of garlic in preventing or treating the common cold. A single trial
suggested that garlic may prevent occurrences of the common cold but more studies are needed to validate this finding. Claims of
effectiveness appear to rely largely on poor-quality evidence.
P L A I N L A N G U A G E S U M M A R Y
Garlic for the common cold
Garlic is popularly believed to be useful for the common cold. This belief is based on traditional use and some laboratory evidence that
garlic has antibacterial and antiviral properties.We looked for studies that investigated the use of garlic for either preventing or treating
the common cold. Of the five studies identified, only one fulfilled the criteria for the review. This study of 146 participants found that
people who took garlic every day for three months (instead of a placebo) had fewer colds. When participants experienced a cold, the
length of illness was similar in both groups (4.63 versus 5.63 days). While this one study was positive, there is a need for large, highquality
randomised controlled trials to support these findings. Possible side effects in this small trial included odour and a skin rash.
More information is needed about the possible side effects of garlic.
There is no information from randomised controlled