Allicin (Stabilized)
The sulphur compound formed when garlic is crushed, and a potent antimicrobial in a test tube. In humans the entire cold-prevention case rests on one trial from 2001 that has never been repeated.
Evidence last reviewed: August 2026
What the science says
- One trial, never replicated Limited evidence
A Cochrane review of garlic for the common cold identified only a single randomized trial meeting inclusion criteria. The reviewers concluded that there is insufficient evidence to recommend garlic for preventing or treating colds, and that more trials are needed.
- The original trial reported fewer colds Limited evidence
That trial gave an allicin-containing garlic supplement or placebo to volunteers over twelve winter weeks and recorded markedly fewer colds in the treated group. Colds were self-reported in a diary, the reporting of methods was incomplete, and no independent group has reproduced it.
- Antimicrobial activity does not transfer to the body Limited evidence
Allicin kills bacteria, fungi and viruses in culture at concentrations that are not achievable in blood after swallowing a supplement. It is also chemically unstable, which is why products advertise an allicin yield rather than an allicin content.
Dosage & safety
Scientific references
Where to buy
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