Dr. Howard Bennett creates elaborate Lego sculptures, juggles squishy balls during office visits and transforms exam gloves into water balloons, but it's his booger and fart jokes that crack up even his grumpiest pediatric patients.

"Kids of any age are curious about their bodies," the pediatrician writes in his latest book, The Fantastic Body: What Makes You Tick & How You Get Sick, "especially if what they're learning about is gross! That's why kids laugh hysterically if someone tells a booger joke or lets out a big, juicy fart in class."

Bennett, who practices in Washington, D.C., has been writing about children's health for years, in books and in a column for The Washington Post. The Fantastic Body includes fun facts about lice, pimples, warts and other nasty stuff, but he also explains to children how muscles work, how you digest food, what's going on inside your brain and heart, how to treat common ailments and how to avoid getting sick in the first place. This interview has been edited for length and clarity.

How did you discover that telling gross jokes could help children feel more comfortable?

Adults are typically scared about what's wrong with them. Children are scared about what you're gonna do to them, but in both cases, patients need to know that you're interested in why they're there, interested in them as people, that you care about them. There's lots of different ways to do that. You don't have to talk about pee and poop. You can talk about the weather, politics, and you can be kind and very serious and still get it across.

It just so happens that part of me never grew up, so pee and poop and that kind of stuff, my patients' parents see that their kids like this, and so they let me go with it because they realize it makes the kids feel more comfortable.

In the adult world, research has shown that if you come into my office, and I spend just a minute talking to you about something unrelated to why you're there, you'll be more satisfied with the visit, and you'll be more likely to do what I'm suggesting you do, so it improves patient compliance. It's not just touchy-feely stuff. It actually has an impact on health care.

Do your strategies work even with very sick kids?

One time when I was in the ER, this child was very scared, and somebody called me over to see if I could do something 'cause I guess I had a little bit of a reputation for being childlike, if not childish. He was in his bed wearing Ernie pajamas and Ernie slippers, and I pulled out my Ernie puppet. I swear I could have put a tube in the child's throat, and he would have said 'Thank you.' He was mesmerized. By taking out Ernie, I showed him that I liked kids, and I liked toys, and if I liked toys, maybe I'm not a jerk.

Do your jokes ever backfire?

At one visit, I was ranting about potty humor, and the mom said, "Dr. Bennett, we don't use potty humor in our house." For the next 20 years, I never used potty jokes with them. Another mom wrote me a letter explaining that my humor is inappropriate and offered to take me out to lunch to teach me how to interact with children. I declined.

I went into the room once with this girl who got hit on the head with a lacrosse ball, and the first thing she said is, "My head really hurts; I don't want any jokes," so I didn't do any. You get a feel for it, but still, anybody can mess up. If people know that your intentions are good, I think it's OK.

When did you start writing books, and how did you decide to write The Fantastic Body?

The first book I did was The Best of Medical Humor in 1991. Then I did Waking Up Dry: A Guide to Help Children Overcome Bedwetting in 2005, and I saw there was a perfect way to put together my writing for kids and my working with kids. You know that standard line about write what you know? It finally sort of came together. The Fantastic Body grew out of my KidsPost columns. There are a lot of gross books out there, but this was the first time anybody put the body, physiology, medical facts and gross stuff all together.

What's your favorite gross fact in the new book?

One of my favorites is a sidebar in the skeleton chapter. When lobsters molt, and they're just these things crawling around with no shell, people in the lobster industry refer to them as turds, so this is perfect. I've got a medical fact, and I've got a gross fact all wrapped into one.

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