What a Split End Actually Is
The hair shaft has three layers. The outermost one, the cuticle, is a sleeve of overlapping keratin scales that protects the cortex underneath. When those scales erode at the tip, from friction, heat, chemical processing, or simply time, the cortex beneath splits lengthwise. That split is structural. The two separated strands of cortex cannot fuse back together. A conditioning mask can coat the outside and make the hair feel smoother for a wash cycle or two, but the moment that coating rinses away, the split is exactly where it was. Trimming is the only intervention that removes the damage rather than concealing it.
