Grapefruit seed extract (GSE), also known as citrus seed extract, is a liquid extract derived from the seeds, pulp, and white membranes of grapefruit.[1] Self-made natural GSE processed in the laboratory without synthetic agents is prepared by grinding the grapefruit seed and juiceless pulp, then mixing with glycerin.[1] Commercially available GSE sold to consumers are made from the seed, pulp, glycerin (and in some cases synthetic preservatives) all blended together.[1] Grapefruit seed extract is sold as a food supplement and used in cosmetics because it is a claimed natural antimicrobial.[2]