What it is
Red 504, indexed as CI 15585 and commonly known as Pigment Red 53, is a synthetic monoazo dye derived from the coupling of diazotized 2-amino-5-chloro-4-methylbenzenesulfonic acid with 2-naphthol. It presents as an odorless yellowish-red to reddish-orange powder with very low water solubility and a melting point around 343–345°C. In cosmetics it functions solely as a colorant. The free acid form (CAS 2092-56-0) and its barium lake salt form (Pigment Red 53:1, CAS 5160-02-1) are both known. The dye is classified IARC Group 3 (inadequate evidence of carcinogenicity), but regulatory concern centers on metabolic reductive cleavage of the azo bond releasing aromatic amine by-products with potential carcinogenic and mutagenic activity. It is prohibited for cosmetic use under EU Regulation 1223/2009 Annex II and was removed from the US D&C approved list in 1988.
Safety & warnings
Red 504 is an azo dye that can undergo reductive cleavage of the azo bond, releasing aromatic amines that are classified as potential carcinogens and mutagens. Regulatory bodies in the EU and the US have prohibited or removed it from approved cosmetic colorant lists due to these concerns. Long-term exposure has been associated in animal studies with blood disorders and spleen sarcoma. The barium lake form (Pigment Red 53:1) adds barium ion exposure as an additional consideration. Risk is elevated for lip and eye-area cosmetics where ingestion or mucous membrane absorption may occur. IARC classifies it as Group 3 (inadequate evidence in humans). The EU lists CI 15585 under Annex II/1301 of Regulation 1223/2009.
Origin & sourcing
Red 504 is produced synthetically via azo coupling chemistry: 2-amino-5-chloro-4-methylbenzenesulfonic acid is diazotized and coupled with 2-naphthol (beta-naphthol) to form the azo chromophore. The barium lake variant (Pigment Red 53:1) is made by treating the acid dye with a barium salt to form an insoluble pigment with improved fastness properties for industrial use.
History
Pigment Red 53 and its lake form were developed as industrial organic pigments in the mid-20th century and saw use in printing inks, textiles, and decorative cosmetics. Regulatory scrutiny intensified following research linking azo dye metabolites to carcinogenicity. The EU Scientific Committee on Cosmetic Products (SCCP) reviewed azo colorants and placed CI 15585 on Annex II (prohibited substances list) of the EU Cosmetics Directive. The US FDA removed D&C Red No. 9 from its approved colorant list in 1988. The JCIA (Japan Cosmetics Industry Association) maintains a positive tar-color list for cosmetics; Red 504 appears in Japanese regulatory color numbering as 赤色504号 (Aka 504-go).
Questions everyone asks
What is Red 504 in cosmetics?
Red 504 (CI 15585, Pigment Red 53) is a synthetic azo dye that produces a yellowish-red to orange-red color. It has historically appeared in decorative cosmetics such as lipsticks and face paints as a colorant.
Is Red 504 safe for use in cosmetics?
Red 504 is prohibited for cosmetic use in the European Union under Annex II of Regulation 1223/2009, and the related D&C Red No. 9 designation was removed from the FDA-approved list in the United States in 1988.
What is the difference between Pigment Red 53 and Pigment Red 53:1?
Pigment Red 53 (CAS 2092-56-0) is the free acid form of CI 15585, while Pigment Red 53:1 (CAS 5160-02-1) is its barium lake salt, an insoluble pigment form used widely in printing inks. Both share the same azo chromophore but differ in physical form and solubility.
Why do some products still contain Red 504?
Red 504 may appear in products manufactured in markets where it has not been explicitly prohibited, or as a contaminant in formulations using related colorants. Research from Indonesia and other countries has identified it as an illegal adulterant found in commercial cosmetics, highlighting the impo