美国国家公共电台 NPR 'Dirt Is Good': Why Kids Need Exposure To Germs

LULU GARCIA-NAVARRO, HOST:

It's summertime. And if you have a young kid, chances are they're covered in a film of sweat and dirt. It can be kind of gross. We went to New York Avenue Park in Washington, D.C., and asked parents how comfortable they are with the yucky stuff.

JEANINE MCGINNISS: Probably I was a little bit more of a germ freak. And then once you have a kid, you start getting comfortable with more germs.

DOROTHEA THOMAS: You know, every possible chance that if there is a germ or whatever, I make him wash his hands.

WENDY CHRISTMAS: I work hard to make sure that they're clean.

GERALD SMITH: Make sure they wash their hands constantly, all the time, soap and water.

GARCIA-NAVARRO: A quick survey there of parents Jeanine McGinniss, Dorothea Thomas, Wendy Christmas, and Gerald Smith. But are we too quick to rush kids to the bath at the end of the day? Our next guest says that dirt is good. Dr. Jack 1 Gilbert is professor of surgery at the University of Chicago, and he's co-author of a book for new parents guiding them through the world of germs, the microbiome and obviously dirt. He joins us from our member station WBEZ in Chicago. Good morning.

JACK GILBERT: Good morning, Lulu.

GARCIA-NAVARRO: Why did you write this book?

GILBERT: Well, as a parent - I have two children now - I can say that when I had my first child, I got a lot of different advice on the kinds of things that I should do to look after my kid. If they have a snotty nose, consider taking antibiotics 2, to make sure their pacifier was always sterilized 4, to sterilize 3 their food and make sure it was always boiled before you gave it to them. And so for me, it was interesting to go back and look at the data, especially after my second child, where I got a lot more lax in terms of how much of that preparation I put in.

And so we went and looked at the literature, went and delved 5 into the science and tried to understand what we actually knew about the risks that our modern-day children could experience from those kinds of exposures. Turned out that most of the exposures were actually beneficial.

GARCIA-NAVARRO: You mentioned a few of them already, but what are some of the main things that parents get wrong?

GILBERT: Some of the main things are over-sterilizing 6 their environment, keeping their children from ever getting dirty. So going out into the backyard and playing in the mud, and then as soon as they're filthy 7, bringing them in and sterilizing their hands with antiseptic wipes and then making sure that none of the dirt gets near their faces. Also keeping them away from animals. It's fine to wash their hands if there's a cold or a flu virus around. But if they're interacting with a dog and the dog licks their face, that's not a bad thing. In fact, that could be extremely beneficial for the child's health.

GARCIA-NAVARRO: Let's get to some of these questions. You tell me good or bad. Hand sanitizer?

GILBERT: Usually bad. Hot soapy water is fine, even mildly warm soapy water is fine. And it's actually probably less damaging to the child's overall health.

GARCIA-NAVARRO: All right, five-second rule. If something falls on the ground, you know, that thing if it's there for under five seconds it's clean, if it's over five seconds you've got to wash it.

GILBERT: The five-second rule doesn't exist. It takes milliseconds for microbes to attach themselves to a sticky piece of jammy (ph) toast, for example. But it makes no difference. Unless you dropped it in an area where you think that could be a high risk of extremely dangerous pathogens, which in every modern American home is virtually impossible, then there's no risk to your child.

GARCIA-NAVARRO: All right. Wash a pacifier or lick it if it falls on the ground?

GILBERT: Lick it every time. A study of over 300,000 children showed that parents that lick the pacifier and put it back in, their kids developed less allergies 8, less asthma 9, less eczema. Overall, their health was stronger and more robust 10.

GARCIA-NAVARRO: And how often should I give my daughter a bath? This is a very important question, by the way, because she hates them.

GILBERT: I know, exactly. Especially when they're small children under the age of 6 months, so infants up to about 18 months, you don't need to get them off every day. In fact, you could go for a couple of days. Wiping down the area with a warm wet cloth. Overall, over-washing can actually damage the skin and lead them to have a higher likelihood of infections and over-inflammatory reactions like eczema.

GARCIA-NAVARRO: One of the things that we are seeing, especially in America, is the rise of allergies. Do you think these two things are linked because we try to protect them so much that, you know, the unintended consequence of that is that actually they are more susceptible 11 to things like allergies?

GILBERT: Absolutely. So the basic premise 12 is that in the past, we would have eaten a lot more fermented 13 foods, which contain bacterial 14 products and bacteria. We would have allowed our children to be exposed to animals and plants and soil on a much more regular basis. Now we live indoors. We sterilize our surfaces. Their immune systems then become hyper-sensitized.

You have these little soldier cells in your body called neutrophils. And those neutrophils, when they spend too long going around looking for something to do, they become grumpy and pro-inflammatory. And so when they finally see something that's foreign, like a piece of pollen 15, they become explosively inflammatory. They go crazy, right? And that's what triggers asthma and eczema and oftentimes food allergies.

GARCIA-NAVARRO: So I was going to ask you just finally to give us some advice. I mean, as a mother, what should I be allowing my daughter to do? And what is still something that I should not allow her to do?

GILBERT: Right. So oftentimes, it's hard to get your kids to eat a healthy diet, right? I know this more than any parent. But I would strongly try and encourage the consumption of more colorful vegetables, more leafy vegetables, a diet more rich in fiber 16, as well as reducing the sugar intake 17. But just generally, allow your kid to experience the world. As long as they're properly vaccinated 18, there's no threat. And they will actually get a stronger, more beneficial exposure.

GARCIA-NAVARRO: Dr. Jack Gilbert. He's the co-author of "Dirt Is Good." Thank you so very much.

GILBERT: Thank you. It's great to be here.

(SOUNDBITE OF PENGUIN CAFE ORCHESTRA'S "DIRT")