Background

The ingredient Methylimidazoliumpropyl p-phenylenediamine HCl (A166) is intended to be used in oxidative hair colouring products up to a maximum on-head concentration of 2%.

For an exhaustive background information, see the article
• Salicylic acid, Hair dyes: four requests for Opinion to SCCS of 2 January 2018

Opinion

1. In light of the data provided, does the SCCS consider Methylimidazoliumpropyl p-phenylenediamine HCl (A166), safe when used in oxidative hair colouring products up to a maximum on-head concentration of 2%?

Although evaluation of the data provided for Methylimidazoliumpropyl p-phenylenediamine HCl (A166) has shown it to be safe, no safety data have been provided for the impurities and the residual solvents that are also present. Analysis of the potential risk carried out by the SCCS according to TTC (Threshold of Toxicological Concern) principles has indicated that the levels of one of the impurities (3-aminopropyl imidazole) and a residual solvent (chloroethane) are above the TTC levels that can be considered safe. Therefore, the SCCS cannot conclude on the safety of Methylimidazoliumpropyl p-phenylenediamine HCl (A166) unless its purity is improved to bring the levels of the impurity and the residual solvent down to below the acceptable TTC levels.

2. Does the SCCS have …