A Cochrane review [Abstract] 1 included 1 study with a total of 146 subjects. This trial assigned volunteer participants to either a garlic supplement (with 180 mg of allicin content) or a placebo (once daily) for 12 weeks. The trial reported 24 occurrences of the common cold in the garlic intervention group compared with 65 in the placebo group (P < 0.001), resulting in fewer days of illness in the garlic group compared with the placebo group (111 versus 366). The number of days to recovery from an occurrence of the common cold was similar in both groups (4.63 versus 5.63). Adverse effects of garlic supplement included rash and odour.
Comment: The evidence is downgraded by imprecise results (limited study size). The trial relied on self-reported episodes of the common cold.
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