Rock the 2025 Minnesota Cosmetology Exam – Flaunt Your Skills and Glam Up Your Future!

The cortex is the layer of the hair that is most affected by chemical treatments. This is because the cortex is the thickest layer, located beneath the cuticle, and is made up of long chains of keratin, a type of protein that gives hair its strength, color, and texture. Chemical processes, such as coloring, perming, or relaxing, penetrate through the cuticle and interact primarily with the cortex, altering its structure and properties. This influence can change the hair's porosity, elasticity, and overall appearance.

The cuticle serves as a protective outer layer, but it does not undergo significant changes from chemical treatments; rather, it can be damaged as a side effect of the chemicals affecting the cortex. The medulla, often referred to as the innermost layer of the hair, is not consistently present in all hair types and has limited influence on color and texture, making it less relevant in the context of chemical processes. Fibrils, which are smaller structures within the cortex, also play a role in strength but are not the primary focus when discussing the effects of chemical treatments. Overall, the cortex's composition and role in hair structure make it the most significantly impacted layer during chemical applications.