These elastin fibers are damaged in stretch marks, causing the ‘scar’ of a stretch mark. What’s so remarkable about stretch marks is how prominent they look, but under a microscope you see almost no difference from normal, healthy skin. If you touch a stretch mark, it feels empty, almost like there is no skin there. Visually and textually the skin is so very different, yet so little has actually changed in the skin.

Why don’t they heal over time?

Stretch marks are a huge problem. The problem with stretch marks is the elastic fibers in skin with stretch marks are damaged, and elastic fibers are the single hardest thing to repair in skin. When you have a wound that’s healing, our body replaces the collagen proteins and all the skin structures that are injured, but the elastic fiber is very difficult to repair. The trouble with stretch marks is that there’s this defect in those fibers. So since our body cannot effectively repair those fibers, the stretch marks do not heal.