An object of the present invention is to provide IL-8 production promoters derived from safe food materials and to provide immunostimulants or preventive or treating agents of infectious disease comprising the IL-8 production promoter. The present inventors have found that a composition comprising, as an active ingredient, at least one plant extract from peppermint, dokudami (houttuynia herb), or licorice promotes IL-8 production, and that a composition comprising, as an active ingredient, at least one compound selected from the group consisting of .alpha.-humulene, .alpha.-pinene, .beta.-pinene, and L-menthol promotes IL-8 production. These IL-8 production promoters can be used in foods and drinks supplemented with immunostimulants or preventive or treating agents of infectious disease.