C.I. 37545 is also known as Azoic dyes. C.I. 37545 is impregnated cotton with an alkaline solution of β-naphthol, then treated it with a diazo solution obtained from aniline, a toluidine, xylidine, naphthylamine, aminoazobenzene or aminoazotoluene, so that particles of an azo pigment were formed and became firmly fixed within the fibre. Sensitisation to PPD on a henna tattoo with cross reaction to azoic dyes. may produce an increase in the frequency of contact dermatitis due to henna mixtures with cross- reaction to related compounds and possibly producing permanent skin changes.