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RENEE MONTAGNE, host:

This is MORNING EDITION from NPR News. I'm Renee Montagne.

STEVE INSKEEP, host:

And I'm Steve Inskeep. With all the advances in medical science, doctors still can't do anything to reverse an allergy to poison ivy. Brushing up against that plant can ruin your summer camping trip and for some people it can ruin a lot more, which is why it's our subject on Your Health this Thursday morning. Reporter Deborah Franklin is covering this story, and Deb, what makes this a big deal?

DEBORAH FRANKLIN: Because 85 percent of Americans are susceptible to developing an allergy to poison ivy. It can last forever, Steve, and because it interferes with the entire life of a person like Lynette Scaffidi(ph), who except for the poison ivy says she has the perfect job.

Ms. LYNETTE SCAFFIDI (Natural Resource Specialist): I really enjoy being out in the woods. I love to weed, which is kind of ironic. You know, I have to weed every day. It's my therapy. It's my time that I actually can think, clearly think, so it just fits.

FRANKLIN: Scaffidi's a natural resource specialist for Montgomery County Parks out in suburban Maryland, and she spends a lot of her days thigh-high in weeds, teaching volunteers to identify and yank or cut out the kudzu and bittersweet and other vines and grasses that are out there choking the forest.

Ms. SCAFFIDI: Well, unfortunately, we don't have to go far.

FRANKLIN: One of the worst offenders is a low-growing tangle of spiky vines with triangular leaves.

Ms. SCAFFIDI: This one right here is called Tearthumb.

FRANKLIN: We bent down for a closer look.

Ms. SCAFFIDI: You can see there's little thorns all up and down each of the stems and on the veins on the back of the leaves. So it tears your thumb when you go to grab it.

FRANKLIN: This vine's got to go, she says, before it swallows up more trees, but thorns aren't the only problem.

Ms. SCAFFIDI: We have poison ivy growing right in amongst the Tearthumb. If you look all over here, that's poison ivy in amongst the Tearthumb.

FRANKLIN: And that's the hitch, or in this case the itch, in Scaffidi's perfect job. She's terribly allergic to poison ivy.

Ms. SCAFFIDI: I have some on my thumb, I've got some on my arm. I've got it all over my feet. I've got it on my palms.

FRANKLIN: And it's more than a nuisance.

Ms. SCAFFIDI: Sometimes I'll take rubbing alcohol, like when I had this really bad patch right here. The pain is so much better than the itch, you know, because the itch drives you nuts.

FRANKLIN: It's not that Scaffidi can't spot poison ivy before she grabs it. She's an expert. She takes disposable wipes into the field and scrubs like a surgeon when she gets home, but she can't control everything.

Ms. SCAFFIDI: My husband will go and pull poison ivy with his bare hands and not get a bit. He's given it to me that way because then he just slightly washes his hands, and then if he touches me I get it wherever he's touched me. So I'm like wash again, wash again, get between your fingers.

(Soundbite of laughter)

FRANKLIN: Even now, nobody really knows why some people, like Scaffidi, are hyper-sensitive to the tiniest smudge of sap or why a few others, like her husband, are immune. But scientists do know what triggers the reaction. It's something in the way the lower layers of skin bind to and interact with a sticky resin in the sap called urushiol.

Jim Marks is a dermatologist at Penn State in Hershey, Pennsylvania, and back in the 1980s Marks thought he was on to something. He'd read accounts of early Americans who'd nibbled on a bit of leaf to become immune to poison ivy.

Now, do not try this at home. Other people who have eaten the plant or extracts of it just end up itching from stem to stern. Still, Marks was intrigued.

Mr. JIM MARKS (Dermatologist): A number of animal studies would indicate if you somehow could avoid the skin, say by injections or by orally, you could induce tolerance to the resin.

FRANKLIN: The most intriguing bit of evidence came not from a lab or the woods but from a factory outside of Philadelphia, a place that grinds up the shells of cashew nuts to make friction dust for the brake linings of cars. Turns out those cashew shells are loaded with urushiol, the same oil that's in poison ivy. Workers in the factory...

Mr. MARKS: Either they got over the rash in about a month or so, or they had to leave the factory.

FRANKLIN: But after that first month of itching, the workers who stayed on were no longer allergic to the cashew shells. Even more interesting to Marks...

Mr. MARKS: They had had a history of getting poison ivy, some of them severely, and then after working in the factory they could roll around in poison ivy and not have problems.

FRANKLIN:

Marks figured that maybe constantly ingesting some of the particles of urushiol in the factory air had somehow helped the workers develop a tolerance to it. That gave him hope that a toned-down version of urushiol in pill form might also induce tolerance.

Chemists were able to come up with a safe pill that worked just the way they'd hoped - in guinea pigs - and at first it seemed promising in people too when they tested it against a sugar pill or placebo.

Mr. MARKS: This one subject who had always gotten bad poison ivy every summer was sure that he had gotten the active because he didn't have poison ivy that summer at all.

FRANKLIN: Unfortunately that wasn't the case.

Mr. MARKS: Indeed, he had been on the placebo.

FRANKLIN: But it's been 20 years since Jim Marks's study with the workers in the cashew factory. So how come scientists aren't any closer to that anti-poison ivy pill?

Dr. ANTHONY GASPARI (University of Maryland): It's very complicated.

FRANKLIN: That's Anthony Gaspari. He's a dermatologist at the University of Maryland in Baltimore, and at least so far he doesn't have any plant allergies.

Dr. GASPARI: I'm a city boy. I grew up in South Philadelphia, so you know, the mean streets of South Philadelphia, there's no poison ivy.

FRANKLIN: Nonetheless, he is interested in the way the skin interacts with the immune system, and it is very complicated, but Gaspari gives it his best shot.

Dr. GASPARI: I tell patients that the skin is armed and dangerous.

FRANKLIN: He says the skin has immune system soldiers, white blood cells lined up and ready for attack against any harmful germ or chemical that might try to break through. That's great for battling bacteria in a cut or a scrape, but in the case of poison ivy it does more harm than good. There's something about urushiol that tricks the immune system.

Dr. GASPARI: It tricks the immune system into saying, boy, this is something really dangerous. We have to remember this, and the next time we see it, we're going to attack it. Now, that memory is present. It's pretty remarkable, and it's stubborn. It can't be turned off.

FRANKLIN: Gaspari says that if scientists could figure out how to get those immune system soldiers to step down when they're not needed, they'd be closer to solving the problems not just of poison ivy but also of rejection in organ transplants, closer to curing immune diseases like lupus or multiple sclerosis.

Dr. GASPARI: Immune tolerance is the Holy Grail of immunology. Methods that work with one kind of allergy don't work with another kind of allergy because one kind of allergic response is trainable. The other is not. Why that's the case, we really don't understand. We don't know yet.

FRANKLIN: So that leaves Lynette Scaffidi back where she started, trying to avoid the plant. And I can tell you it's easier said than done.

Ms. SCAFFIDI: Now, Deborah, you just kicked poison ivy, just so you know.

(Soundbite of laughter)

FRANKLIN: I've got to get some wipes.

INSKEEP: We've been listening to a walk through the woods with reporter Deborah Franklin. And Deb, for those people who are itchy just listening to this story, are wipes really the only weapon we've got?

FRANKLIN: Well, there's still nothing that really reverses that sensitivity. Once you've got it, you've probably got it for life.

INSKEEP: Okay, so what if you do get exposed to poison ivy?

FRANKLIN: The best thing to do is get it off fast. That's the goal, so rubbing alcohol is a good thing, anything that cuts the oil, really, and keeps it from getting to the skin. But if you don't have any rubbing alcohol in the woods, when you get back to the house, soap and water, any kind of soap that has a little a detergent in it. Dish soap, that works fine.

INSKEEP: Okay, well, what if I just want to prevent being exposed in the first place, and I don't really want to wear, you know, an asbestos suit or whatever it is I would have to wear - what do I do?

FRANKLIN: You're in luck, Steve. There is a goop, Ivy Block. I brought some along here, you might - here.

INSKEEP: Oh, this white bottle you've got here? Thank you.

FRANKLIN: Shake it up. Make sure you shake it up.

INSKEEP: Okay.

FRANKLIN: Squirt a little on.

INSKEEP: Oh, it is kind of goopy, isn't it?

FRANKLIN: See what you think.

INSKEEP: It doesn't smell like much, I'm happy to say.

FRANKLIN: Somebody told me it smelled like camping, but I don't know.

INSKEEP: It smells like the great outdoors.

FRANKLIN: But in this Ivy Block, this lotion, it forms a barrier so the urushiol doesn't get to the skin.

INSKEEP: Okay, not much hope, but some. Deborah Franklin, thanks very much.

FRANKLIN: Thank you, Steve.

(Soundbite of song, "Poison Ivy")

INSKEEP: For some more tips on preventing poison ivy, got to NPR.org.

(Soundbite of song, "Poison Ivy")

THE COASTERS (Music Group): (Singing) She's pretty as a daisy, but look out, man, she's crazy. She'll really do you in if you let her get under your skin.

INSKEEP: This is NPR News.

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