Herbal Hair Dye Shampoo with Effective Hair Coloration, Color Durability, Low Irritation Potential, and Favorable Hair Morphology

Background: Chemical hair dyes provide effective and durable coloration but are frequently associated with hair damage and irritation. Therefore, this study aimed to develop herbal-based hair dye products that combine effective coloration with low irritation potential. Methods: The combination of Lawsonia inermis, Clitoria ternatea, and Indigofera tinctoria was incorporated into different formulations (solution, shampoo, and conditioner) and evaluated for physicochemical properties, accelerated stability, and hair dyeing performance. The effects of herbal mixture concentration (10, 20, and 30% w/w) were further investigated for hair dyeing, foaming properties, washing fastness, and color stability under ambient natural-light conditions. The most suitable shampoo was evaluated for irritation potential using the hen’s egg test–chorioallantoic membrane (HET-CAM) assay, hair morphology by scanning electron microscopy, and hair chemical characteristics using Fourier-transform infrared (FT-IR) spectroscopy. Results: Herbal hair dye formulations were successfully developed. Although the solution achieved the greatest hair dyeing performance, the shampoo provided more practical convenience. Increasing the herbal mixture concentration significantly enhanced dyeing performance, with the 30% w/w formulation producing the greatest dyeing performance, with stable color maintained after five washing cycles and excellent resistance to light-induced fading. Interestingly, the herbal shampoo exhibited significantly lower irritation potential than the chemical hair dye shampoo (irritation score: 4.9 ± 0.4 vs. 14.2 ± 0.4, p < 0.05) and better-preserved hair cuticle integrity. FT-IR analysis showed retention of major keratin-associated bands, indicating no complete disruption of the fundamental keratin structure. Conclusions: The herbal hair dye shampoo offers a promising alternative to conventional hair dye, providing effective and durable hair coloration with favorable preservation of hair surface morphology and lower irritation potential.