A flavour composition comprises at least 0.5% by weight of one or more of the following group A materials: cinnamic aldehyde, basil oil, tarragon, cis-3-hexenyl acetate, cis-3hexenol, orange oil, lime, citral, and damascone; and at least 3% by weight of one or more of the following group B materials: anethole synthetic, alcohol C10, eucalyptol, methyl salicylate, clove bud oil, carvone laevo, benzyl benzoate, thymol, benzaldehyde, benzyl formate, ethyl salicylate, eucalyptus oil, ionone alpha, iso amyl acetate, rosemary oil, cardamom oil, ginger, eugenol, camomile oil, spearmint, and peppermint. These materials have been identified as being capable of inhibiting the growth of Porphyromonas gingivalis or the protease (arg-gingipain) activity of Porphyromonas gingivalis, and so to possess hitherto unappreciated antimicrobial properties. The invention thus enables compositions to be defined comprising flavour materials that enhance the antimicrobial efficacy of known antimicrobial agents against micro-organisms or metabolic processes associated with gum diseases. The invention also provides a consumer product, particularly an oral or dental care product, including such a flavour composition; a method for reducing or preventing gum disease; and use of the flavour compositions for reducing or preventing gum disease.