Identification of contact allergens in C.I. Solvent Red 23 (commercial Sudan III) by chemical analysis and animal testing

Abstract

C.I. Solvent Red 23, commercial Sudan III, is widely used in cosmetic products. Chemical analyses and guinea pig sensitization tests were carried out to identify its contact allergens. In the Magnusson & Kligman guinea pig maximization test, C.I. Solvent Red 23 showed 20% positive reactions. By conducting chemical analyses with HPLC and GLC, 2-naphthol (82 ppm), azobenzene (48 ppm), Sudan I (570 ppm) and many unknown impurities, as well as the main constituent pigment Sudan III (87%), were found. The chemical structure of one unknown impurity was identified as an isomer of Sudan III. We found that purified Sudan III showed no positive reaction, while the isomer elicited 30% positive reactions, in the same guinea pig test. Furthermore, cross-sensitization with p-phenylenediamine was investigated using the guinea pig test. Animals sensitized with p-phenylenediamine also showed positive elicitation reactions with purified Sudan III. From these results, the contact allergenicity of C.I. Solvent Red 23 is considered to be due to impurities, including the isomer of Sudan III, 1-(o-phenylazophenylazo)-2-naphthol. Positive reactions to Sudan III previously demonstrated in hairdressers are due to cross-sensitivity with p-phenylenediamine.

Cosmetic Analysis Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI)

“…Sudan III was chosen because of its potential carcinogenic risk and because it is also a common dye for cosmetics [ 21 ]; in this case, it was stated as an ingredient on all the labels as CI 21600 (color index) and/or Solvent Red 23 (commercial name). The health risks associated with a possible carcinogen in a nail polisher formulation are due to accidental ingestion by nail biting or even when cooking or baking.…”

Sensitive Method for the Identification of Potential Sensitizing Impurities in Reaction Mixtures by Fluorescent Nitrobenzoxadiazole-Labeled Glutathione

“…For the protection of workers and consumers, skin-sensitizing potentials of chemicals in manufacturing processes, including raw materials, intermediates, and products, must be assessed at an early stage of product development. It is known that some unexpected minor impurities with strong skin-sensitizing properties are generated as byproducts and can contaminate the nonsensitizing target product, which can then give the entire sample strong skin-sensitizing properties . In such cases, it is not easy to identify the component that is the main cause of skin sensitization.…”

“…In such cases, it is not easy to identify the component that is the main cause of skin sensitization. In previous research with the commercial dye Sudan III, each component was fractionated by column chromatography and skin sensitization with each fraction was evaluated to identify the main skin sensitizer . Other studies have also used chromatographic separation before evaluation to identify the skin-sensitizing components in a German chamomile ( Matricaria chamomilla ) extract and a Commiphora myrrha (myrrh) extract used as a natural skin remedy …”