Wet Response

The wrinkling effect is initiated by sympathetic nervous system activation, which triggers vasoconstriction of digital blood vessels beneath the skin.

This response reduces the volume of the dermal tissue, while the stratum corneum—especially in glabrous skin like fingertips—absorbs water and swells, creating a mismatch in tension.

The reduced support underneath, combined with the expanded outer layer, causes the skin to buckle into characteristic wrinkles.

This is not a passive osmotic process, but a coordinated autonomic response, confirmed by the absence of wrinkling in denervated fingers.