What is the term for hair that is resistant to chemical treatments?

The term for hair that is resistant to chemical treatments is low porosity hair. Hair porosity refers to the hair's ability to absorb and retain moisture. Low porosity hair has tightly packed cuticles, making it difficult for moisture and chemical products to penetrate the hair shaft. As a result, this type of hair often resists chemical treatments, requiring more effort or specific techniques to achieve desired results.

In contrast, high porosity hair has more gaps and holes in the cuticle layer, allowing for easier absorption of substances, but it can also lead to loss of moisture. Medium porosity hair strikes a balance between the two, absorbing and retaining moisture and chemicals more effectively. Normal porosity hair suggests a balanced level of porosity, but low porosity specifically refers to resistance to chemical processes. Thus, the correct identification of low porosity hair is key for understanding how to approach hair treatments effectively.