What type of hair is most resistant to chemical treatments?

Coarse hair is considered to be the most resistant to chemical treatments due to its thicker cuticle layer and the overall structure of the hair shaft. The thicker cuticle provides a more robust barrier against chemicals, making it more challenging for them to penetrate and alter the hair's internal structure, which is necessary for treatments like coloring or perming.

In contrast, fine hair has a much thinner cuticle, which can make it more susceptible to chemical treatments, allowing them to affect the hair more readily. Medium hair falls somewhere in between but generally tends to be less resistant than coarse hair. Curly hair can vary significantly in its texture and porosity, leading to mixed resistance to treatments depending on the specific type of curl and its characteristics. Overall, coarse hair's structural properties make it inherently more durable against chemical changes.