Defects trigger skin boundary cracks

This proposed hypothesis asks why the first cracks form at the edge of a dried skin patch, damage that may accumulate as skin moves. It places the trigger in the stratum corneum, skin’s outer load-bearing layer: a rare pre-existing weak spot could open first as drying and repeated bending load the edge. With stress history, hydration and cycle count matched, a boundary twice as long should have a crack-free probability equal to the square of the shorter edge’s probability. First cracks should begin near mapped weak spots. A test would map defects, vary edge length and count cycles to first cracking. It would require three-dimensional microstructure imaging, spatially resolved mechanical measurements, cyclic-loading response characterization, first-failure statistics and histological confirmation.