Erythrosine: a red dye that continues to be utilised in Argentina. How much evidence is required before precautionary measures are implemented?

Abstract

Erythrosine (FD&C Red No. 3; E127) is a synthetic xanthene food dye bearing four iodine atoms, approved as a food colourant in the United States since 1907. Despite a progressively accumulating toxicological dossier documenting thyroid follicular-cell adenomas, reproductive impairment, genotoxicity, hepatorenal injury, neurotoxicity, and gut dysbiosis, its food use persisted for over a century. In 1990 the FDA applied the Delaney Clause to ban erythrosine from cosmetics and externally applied drugs, yet paradoxically exempted food use on the basis of an indirect, species-specific carcinogenic mechanism. That exemption persisted unchallenged for more than three decades, until a 2022 CSPI petition, the California Food Safety Act (AB 418, 2023), and the federal FDA ban (January 2025) finally closed the regulatory gap. This work synthesises erythrosine's hazard evidence across nine physiological systems, reconstructs its regulatory history, and identifies critical knowledge gaps, particularly the emerging role of erythrosine-induced gut dysbiosis in propagating systemic neuroinflammation via the gut-brain axis. The erythrosine trajectory offers a paradigmatic case of how inconsistently applied bright-line regulatory rules can delay protective action by a generation.