What type of hair is most resistant to chemical treatments?

Coarse hair is characterized by its thicker diameter and structure, which often makes it more resistant to chemical treatments. This resilience is due to the tightly packed cuticle layers, offering greater protection against chemicals used in processes like perming, coloring, and relaxing. Coarse hair typically absorbs less moisture and chemicals compared to finer hair, which can be more porous and susceptible to damage during treatments.

In contrast, fine hair generally has a smaller diameter and can be more fragile, making it more susceptible to chemical services. Medium hair has a balance between the two but can also present challenges with chemical processing depending on its porosity. Curly hair can vary widely in texture and porosity, but it does not inherently denote resistance compared to coarse hair, which is generally recognized for its durability against chemical treatments.

Thus, coarse hair's structural characteristics contribute significantly to its ability to withstand chemical alterations, making it the most resistant type among the options presented.