Why do your fingers and toes wrinkle in the bathtub?

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Dear Cecil: Can you please tell me why your fingers and toes wrinkle in the bathtub, but the rest of your body doesn’t? Rachel F., Chevy Chase, Maryland

Cecil replies:

What my body does or doesn’t do in the bathtub is no business of yours, Rachel. However, speaking in generalities, I might note that the top layer of the skin is composed of toughened, scaly cells collectively known as the stratum corneum. On most of the body, this layer is quite thin, just .015 of a millimeter, but it’s 40 times as thick, or 0.6 of a millimeter, on the soles and palms. Normally the stratum corneum is relatively dehydrated, but it absorbs moisture and swells up when soaking. This swelling occurs throughout the soles and palms, but it’s most noticeable in the fingers and toes because of their restricted dimensions. In extreme cases, e.g., so-called immersion foot syndrome, which sometimes occurs among soldiers whose feet stay wet for prolonged periods, the entire sole can wrinkle up and become painful to walk on. The principle is the same in any case. Since the underlying tissue doesn’t absorb water, the stratum corneum can’t spread out and it buckles like asphalt on the highway in the summer sun.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.