Coloring agents have been around since ancient times, and there is no doubt consumers are heavily influenced by the color of a product. Colorants are often found in lipstick, makeup, nail polish, perfumes, hair dyes, soap, shampoos, creams and even mouthwash—the list is endless.
The most significant colorants in use belong to different chemical classes, including: azo compounds, triarylmethane, anthraquinone, xanthene and phthalocyanine.1 These organic colorants have been heavily scrutinized throughout history due to concerns about potential toxicity to humans and the environment. Several of the colorants in these groups have been banned or restricted by country over time, and the list continues to grow. Formulators, manufacturers and consumers are interested to know the next compound to join this growing list of concerning colorants. Some of the most recent developments regarding the safety of colorants are highlighted below.
Solvent Red 23
This colorant (CAS 85-86-9, CI 26100, D&C Red No. 17) has been on the radar of regulators in a number of countries with some new and important developments. In Canada, Health Canada’s Cosmetic Ingredient Hotlist is being revised to include the organic colorant solvent red 23.2 This ingredient can be found in hair grooming products, dyes, anti-wrinkle creams, shampoos, makeup, nail polish removers, tanning products, shaving creams, face paint and fragrances.3, 4
Solvent red 23 has been reviewed by the Canadian government and concluded to have genotoxic and carcinogenic health effects related to oral exposure.2 It is proposed that this ingredient will be prohibited in cosmetic products intended for use on or around mucosal membranes such as eyes, nose and mouth.2 There will also be additional label warnings required for hair dyes containing this colorant, informing consumers to not use the product for eyelashes or eyebrows or around mucosal membranes.2 Health Canada’s proposal aligns nicely with the restrictions on this ingredient in the United States and the European Union, with minor differences. In the United States, the U.S. Food and Drug Administration (FDA) has additional certification requirements for solvent red 23.5, 6 In Europe, this ingredient has been under a microscope by the German government, where concerns are based on solvent red 23 being an azo dye that can form carcinogenic amines (e.g. 4-aminoazobenzene) upon metabolism in the gut.7 The Scientific Committee on Consumer Products (SCCP) concurs with the German government that solvent red 23 may pose an issue to consumer health, but does not have significant data to be conclusive.7 Despite Germany’s argument and SCCP's supporting opinion, this colorant still remains on the EU’s acceptable colorant list as long as certain purity requirements are met and it is not to be used in products applied on mucous membranes.8