European commision's SCCS Scientific Advice on the Safety Assessment of Hair Dye Basic Blue 99 (C059) – Submissions IV and V

On November 17, 2025, the European Commission’s Scientific Committee on Consumer Safety (SCCS) concluded that Basic Blue 99 is not considered safe for use as an ingredient at 1% in non-oxidative hair dye formulations, as the collective evidence indicates a potential for genotoxicity. Basic Blue 99 is a mixture of substances with significant variability in composition between batches, and while recent manufacturing improvements have stabilized the main constituents to over 80%, the proportion of the second main constituent differs tenfold between old and new batches, rendering previous toxicological data less relevant for current batches. The total impurity content has decreased from about 35% to 15%, but the impurity profile has changed, with some impurities of potential toxicological impact increasing. In silico studies suggest that major impurity families do not present significant genotoxic or carcinogenic concerns for humans, but minor families with quinone groups raise genotoxicity alerts, and some impurities have plausible genotoxicity and carcinogenicity alerts according to DEREK Nexus and Leadscope models, which are not conclusively dismissed as irrelevant for humans. Stability studies were not fully submitted, and the SCCS emphasizes that stability under use conditions must be evaluated with the same HPLC-PDA method used for impurity analysis. Many submitted toxicological studies used batches that do not match current specifications, making their results less relevant, and the dermal absorption study was considered inadequate due to methodological limitations and non-representative batch use. The SCCS regards Basic Blue 99 as a skin sensitizer, with documented cases of both delayed-type and immediate-type contact allergic reactions in humans. Overall, the SCCS remains concerned about the lack of robust toxicological data for current batch specifications, the potential for genotoxicity, and skin sensitization, and notes that the impurity profile and composition variability require further clarification and supporting data. The SCCS considers the current batch specifications under consideration an alert for the risk of immediate-type hypersensitivity reactions, and thus, does not regard Basic Blue 99 safe for use in non-oxidative hair dye formulations at 1% concentration.