The ingredient with the INCI name ‘Sodium Bromothymol Blue’ and chemical name ‘Sodium α- (3-bromo-5-isopropyl-4-oxo-2-methyl-2,5-cyclohexadienylidene)-2-(3-bromo-4-hydroxy-5- isopropyl-2-methylphenyl)toluenesulphonate’ (CAS No. 34722-90-2, EC No. 252-169-7) is a weak acid in solution and thus exists in ionized and non-ionized forms that result in the appearance of different colours. Sodium Bromothymol Blue is intended to be used as a hair dye in non-oxidative hair colouring products with a final on-head concentration up to 0.5%…
