Piper methysticum leaf/root/stem extract is the cosmetic ingredient name for a material derived from the leaves, roots, and stems of the Piper methysticum G. Forster plant, commonly known as kava kava. This and other kava-derived ingredients are used as skin-conditioning agents at concentrations from 0.0001% to 0.1%. The Food and Drug Administration issued a consumer advisory in 2002 expressing concern about liver damage in individuals who have ingested kava products. The available oral toxicity data support the concern about liver damage on ingestion but do not resolve the question, for example, whether these ingredients would be substantially absorbed through the skin. Other data needs are described, including toxicology data for yangonin, methysticin, and kavain, which may be present in kava-derived ingredients. Accordingly, the available data are insufficient to support the safety of these ingredients in cosmetics.
