What is the outermost layer of the hair shaft called?

The outermost layer of the hair shaft is called the cuticle. The cuticle consists of thin, flat cells that overlap like the shingles on a roof, providing a protective layer for the inner structures of the hair. This layer plays a vital role in safeguarding the hair against environmental damage and chemical treatments. The condition of the cuticle significantly affects the hair's overall health and appearance; a healthy cuticle can result in shinier and smoother hair, while a damaged cuticle may lead to issues like frizz and split ends.

Understanding the structure of the hair is crucial for haircolorists, as the cuticle must be taken into account when performing color treatments. For effective penetration of hair color, the cuticle must be properly opened through processes such as the application of heat or chemical treatments. By focusing on the integrity of the cuticle, professionals can ensure better results and minimize damage during coloring services.