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Why Do Your Fingers And Toes Turn Wrinkly In The Tub?

Why do your fingers and toes turn wrinkly in the tub? No one really knows, but in this episode of 'But Why', we learn two of the theories and answer a bunch of your body questions!

Why do your fingers and toes turn wrinkly in the tub? Why are people ticklish? How do you get freckles? Why do some people have birthmarks? How do our hands feel things? Are humans animals? Why don't humans have tails? Why do we need food and water to survive? Why do our nose and ears keep growing? How do bones connect together? We're talking about our weird and wonderful bodies with Dr. Lori Racha, a pediatrician at the University of Vermont.


"Why do your fingers and toes turn wrinkly in the tub?" — Greta 7, East Middlebury, Vt. and Gwenivere, 7, from Fairlee, Vt.

"There is no general agreement of why this occurs. There are a couple of different theories (and theories are just ideas of why this happens.)

The skin is made up of two kinds of layers, an outer layer called the epidermis and a deeper layer called the dermis. It's the outer layer, the epidermis, that's involved with getting wrinkly in the tub. This doesn't happen immediately, when you go swimming or you go in the bathtub and it's usually you've been in there for 20 minutes or so when you start to notice it.

"In this outer layer of the epidermis is something called keratin and so keratin is, its job is to keep your skin kind of strong and together and to also keep it moist. Now keratin gets old with time, it can die and it's in your skin. It's just kind of sitting there as these dead cells. And when those dead cells get subjected to water, one theory is that they kind of absorb water again almost like a sponge. And as that starts to swell it forms some wrinkles.

"And so my next question was will if we have skin everywhere and we have keratin and this layer of our skin everywhere, why is it just our hands and feet? And so looking at that a little bit more closely, I found out that our hands and feet are the part of our body that do the most work. And so they have the thickest layer of keratin. And so it has the greatest opportunity to swell when it's in the water so that made a lot of sense to me.

"A different theory [suggests] that when we have wrinkly skin our ability to pick up objects especially when our hands are wet is much improved. It's kind of like having good tread on your tires on a rainy day, that you don't slip and slide as much and that this could be something that our autonomic nervous system does. The autonomic nervous system is all of the things that are being done in your body that you don't have to tell it to do. So you don't have to tell your heart to start, to keep beating. You don't have to tell your body to breathe. These are all things that your body can do on its own. And so the autonomic nervous system might just sense you're in a slippery environment, it would be better for you to have better tread and may cause the skin to wrinkle just of its own." 

Credit VPR
Greta 7, East Middlebury, Vt. wants to know why our hands get wrinkly in the tub. Gwenivere from Fairlee, Vt. had the same question. Jack from Maplewood, N.J. wants to know how people get freckles?

"How do you get freckles?" — Jack, Maplewood, N.J.

"Freckles are just pigmented areas of your skin and so pigment means contains color and most of the time freckles are kind of a tan or brown color and you may notice that if you have freckles that they get darker when you see more sun. So usually in the summer people will say their freckles are darker and then they get lighter during the winter and then also over time. Younger kids tend to have more freckles than you do when you are older. So for some kids if you're bothered by your freckles you may find that they become less over time.

"Everyone has a certain amount of what's called melanin in their skin and that's the chemicals that kind of determines the pigment, or color, of the skin and that changes when it's exposed to sunlight. When you get more sunlight the melanin starts to produce a darker pigment. In individuals, especially folks who have light-skin, blond hair, red hair and very light skin, they tend to be more prone to freckles than people of darker skinned and darker hair. Those people will tend to get more sunburns too, so we always say it's important to protect your skin when you're outside and use some sunscreen and avoid those times of day when it's most, the sun is most strong which is usually early afternoon."

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In this episode we answer questions from Allegra, 8, in Orange County, Calif., Miles from North Kansas City, Mo. and Avery, 9, from Middlebury, Vt.

"Why are people ticklish?" - Miles, 7, Kansas City, Mo.

"I think the best way to explain it is to think about what's actually happening with a tickle. So you're activating two different parts of your brain when you're getting tickled. So again we've been talking about the skin and these nerve cells collecting information. And so you have one part of the brain that's receiving information about a touch. There's another part of the brain that is kind of interpreting. How do I feel about this touch? And so the two parts of the brain that are collecting this information have really fancy names. The part of the brain that recognizes the touch or pressure is called the 'somatosensory cortex' and so it has sort of a map of the body in the brain. It's saying if I'm tickling you in your belly it's saying I'm receiving pressure, or this tickling feeling in that area.

"Then the other part of the brain that's interpreting how I feel about it, about this pleasant sort of feeling is called the 'anterior cingulate cortex.' When those two areas are activated at the same time, they're both getting messages, you feel a buildup of pleasant feelings which results in giggling. If you try to tickle yourself this doesn't work."

— Dr. Lori Racha, University of Vermont Medical Center

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Listen to the full episode to hear questions from Brady, 7, Hinesburg, Vt.; Steve, 5, from Dallas, Texas; Natalie from Phoenix, Ariz.; Lili, from South Burlington, Vt.; and Eve, 6, from Evanston, Ill.

Listen to the episode for answers to more of your body questions.

Read the full transcript.

Melody is the Contributing Editor for But Why: A Podcast For Curious Kids and the co-author of two But Why books with Jane Lindholm.
Jane Lindholm is the host, executive producer and creator of But Why: A Podcast For Curious Kids. In addition to her work on our international kids show, she produces special projects for Vermont Public. Until March 2021, she was host and editor of the award-winning Vermont Public program Vermont Edition.
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