Which hair type is most resistant to chemical treatments?

Coarse hair is the most resistant to chemical treatments due to its structure and thickness. Coarse hair typically has a larger diameter and a more robust cuticle layer compared to fine and medium hair types. This structural integrity means that the hair can be more resilient against the chemical processes involved in treatments like perming, coloring, or relaxing. While coarse hair can indeed undergo these treatments, it may require higher concentrations of chemicals or longer processing times for the treatment to take effect fully.

Fine hair, by contrast, is generally more susceptible to damage from chemicals due to its smaller diameter and thinner cuticle layer. It can also absorb chemicals more quickly, leading to a greater risk of over-processing. Medium hair, while a bit more resilient than fine hair, still doesn't match the resistance of coarse hair. Curly hair can present unique challenges but isn’t specifically known for its resistance to chemical processes in the way coarse hair is. Therefore, when considering resistance to chemical treatments, coarse hair stands out as the most resilient.