From ABC Science Online, Ask an Expert, 20 August 2012:
Q: Why doesn’t the skin on my fingers and underfeet go wrinkly as my grandchildren’s skin does when in the swimming pool for a long time? It used to when I was younger. I am 66. Is there something that happens to our skin as we age so that we don’t?— Lyndal.
A: One of the extraordinary properties of skin is its ability to maintain its integrity even after hours of soaking in a swimming pool or a hot bath.
This soaking makes the outermost layer of skin double or triple in size as its cells swell, causing our skin to buckle and wrinkle.
However as we age, our skin becomes thinner so even though this outer layer still swells just as much, there is less of it to start with and therefore less wrinkling.
The reason skin gets wrinkly instead of simply dissolving away is because of the complex structure of a protein called keratin in the outermost layer of skin cells, says mathematician and physicist Dr Myfanwy Evans, from the University of Erlangen-Nürnberg in Germany. Read more here.