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Week: 531.4 Guest: Dr. James Nethercott, Prof. Dermatology/Epidemiology, Univ. Of Md. School of Medicine Topic: Poison Ivy- How we get it? Host: Steve Girard

NEMA: My neighbor's got it, my brother's just getting over it....but his daughter's got it, bad. The end of summer's not going quietly, not without the scratching and unpleasantness of poison ivy. Dr. James Nethercott, professor of Dermatology and Epidemiology at the University of Maryland School Medicine is with us today..

NETHERCOTT: Poison Ivy is one of a group of plants called toxiderma plants. It's not the only one, by the way...poison ivy is part of a family that includes poison oak, and poison sumac..which looks somewhat different, but have the same chemical in them, called rushiol, which causes the allergic reaction. You are not allergic to the plant unless you've been exposed to it, and if you've been exposed, you may acquire an allergy to this chemical in the plant... not everyone does, but 80% of people, if they're exposed appropriately, will become allergic to it. Now, if you have become allergic to it, and you are exposed again, sometime in the order of 24 to 48 hours after that exposure, you are likely to develop an acute reaction in your skin, because your body recognizes this chemical in the plant as foreign, and produces a reaction to it, characterized by redness, swelling, blister formation, itching...and then it goes on to weep and heal. The process can take probably on the order of three to four weeks to go away completely in most people because, your skin turns over about once a month, and it takes that long to remove all the resin out of your skin once you're exposed.

Now, the other thing is, that if you get it very severely, you get many spots on your body, you may go on to get something called an auto sensitization dermatitis, which is to say, if you get many, very severe areas of blistering on your skin, you can actually get a reaction that looks like measles... that spreads all over your body. Many people think that means they must have spread it around. They, by the way, have not done that. What that means is that, y'know, if so many parts of your body are inflamed, the rest of it can kind of go out in sympathy with the parts that are very inflamed.

NEMA: Is it necessary to see a doctor?

NETHERCOTT: Well, if they only get it in two or three places on their skin, its not a major thing...I mean if you have two or three patches on your arm or your leg, you can simply treat this by compressing this with salt and water. And applying calamine lotion...not Caladryl, but calamine...and that's usually quite effective, it'll dry it up, and over a few weeks it'll go away. If its more extensive than that, they should seek medical advice, and the most definitive way to treat this is to take pregnazone pills by mouth....this works very well, it will oblate the attack, stop it within 48 hours usually. But the key is to keep taking it for about three weeks, because if you stop it prematurely, what happens is that it bounces back because the resin is still in the skin and the process will start again.

NEMA: Since you've had many papers published on the subject of contact dermatitis...I'll bet you know about how we can get rid of the stuff.....

NETHERCOTT: Rather than sending someone else to go out and pull it all out so that they become allergic to it as well, you can spray it...Roundup, for instance, which you can buy at the local hardware store, is quite effective. Or you might want to get a professional in to spray it for you.

NEMA: Poison ivy can grow as a plant, bush or vine....but the determining factor is that its stems end with three shiny leaves...poison oak also has the three leaf structure, but the leaves are serrated, like oak leaves. Poison sumac has two opposing rows of leaflets, and one at the tip of the stem. I'm Steve Girard.

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Last modified: November 01, 2021