Recurrent aphthous ulcer (RAU) is the most common ulcer of oral non-keratinized mucosa, but the treatment is always limited at present. Considering the multifactorial etiology of RAU, a novel therapeutic agent with multi-bioactivties should be presented. Garlic has been recognized as a favorable natural medicine against a large number of pathologic conditions. The major component of garlic is allicin, which could effectively decrease inflammatory factors secretion, reduce the migration of neutrophils, inhibit bacterium and virus, antagonize oxidation and regulate immunity. By these bioactivities of anti-inflammation, anti-microbial activity, anti-oxidation and immunomodulation, the allicin may be an effective therapeutic candidate to control the pain, promote ulcer healing and prevent the recurrence of RAU.