What is the main function of keratin in hair?

Keratin serves as the primary structural protein in hair, providing both strength and structure. This fibrous protein is essential for the development of the hair's shaft, giving it the resilience necessary to withstand physical stress and environmental factors. The presence of keratin helps maintain the integrity of hair, ensuring it remains strong and less prone to breakage.

Although keratin does play a role in overall hair health, its principal function is to act as a building block, forming the fibers that make up the hair strand. While other options touch on important aspects of hair care, such as color, moisture retention, and UV protection, these are secondary functions that are not directly attributed to keratin's primary role in providing strength and structural support.