Assessing the dyeing efficiency and irritation potentials of plant hair dyes: A multi-analytical in vitro approach.

Abstract

The interest toward dyeing hairs with plant colorants has grown in popularity considering its low-toxic nature. However, researches reporting plant hair dyes are limited and the potential adverse effects of irritation are unclear. This study is aimed to provide an avenue by which to more accurately assess the dyeing efficiency and irritation potentials of plant hair dyes. Four extracted plant colorants were incorporated in hydrogel hair dyes that were directly applied on unbleached gray human hairs. Their dyeing performances and the effect of an iron (Ⅱ) mordant were photometrically measured in CIELab coordinates and color strength. The eye and skin irritancy was assessed by combining various in vitro methods, including bovine corneal opacity and permeability (BCOP) assay in combination with histopathological analysis, Hen's egg test on chick chorioallantoic membrane (HET-CAM) and a test on reconstructed human epidermis models. The investigated hair dyes exhibited desirable dyeing efficiency on human hairs. Post-treatment with the iron (Ⅱ) mordant caused a significant increase in color strength with subtle changes to the hue of dyed color. In the irritation testing, the four hair dyes were categorized as slight-to-mild eye irritants but possessed no skin irritation potential, while the mordant was determined as a non-irritant. The results demonstrate the efficacy of a multi-analytical approach for in vitro assessment of various plant colorants for hair dyeing. The investigated plant extracts are suitable for producing viable colors on human hairs and may serve as a low-irritating alternative to the synthetic hair dyes.