Yarrow (Achillea Millefolium) Extract is an extract of the yarrow plant, Achillea millefolium, supplied in polypropylene glycol, which is reported to function as a "biological additive" in cosmetic products. Sesquiterpene lactones, polyacetylenes, simple coumarins, and flavonoids have been identified among the many components of A. millefolium. Yarrow Extract was reportedly used in 65 cosmetic formulations. Historically, Yarrow (Achillea Millefolium) Extract was reported to be used at concentrations of < or =25%, but recent data indicate that this ingredient is supplied with actual Yarrow (Achillea Millefolium) Extract content of 2% to 25% and used at concentrations of 0.5% to 10%. Only limited toxicity data were available. Guinea pigs were sensitized to crude extracts of the whole plant and the flowers of A. millefolium. A. millefolium tea was weakly genotoxic in a somatic mutation and recombination test using Drosophila melanogaster. In clinical testing, product formulations containing 0.1% to 0.5% of ingredient that actually contained 2% of Yarrow Extract were generally not irritating. In provocative testing, patients reacted to a Compositae mix that contained yarrow, as well as to yarrow itself. Also in clinical testing, a formulation containing 0.1% Yarrow (Achillea Millefolium) Extract (2% Yarrow in propylene glycol and water) was not a sensitizer in a maximization test and alcoholic extracts of dried leaves and stalks of A. millefolium did not produce a phototoxic response. These data were not considered sufficient to support the safety of this ingredient in cosmetics. The types of data (all testing is to be performed on cosmetic-grade ingredients) still required include (1) ultraviolet (UV) absorption data, if absorption occurs in the UVA or UVB range, photosensitization data are needed; (2) gross pathology and histopathology in skin and other major organ systems associated with repeated exposures; (3) reproductive and developmental toxicity data; (4) two genotoxicity studies, one using a mammalian system, if positive, a 2-year dermal carcinogenicity assay performed using National Toxicology Program (NTP) methods may be needed; and (5) clinical sensitization testing at maximum concentration of use. In the absence of these data, it was concluded that the available data are insufficient to support the safety of Yarrow (Achillea Millefolium) Extract for use in cosmetic products.