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Ep 25: Poison Ivy & Other Nemeses

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Ep 25: Poison Ivy & Other Nemeses

Jun 10, 2022
Whether you're more acquainted with the pesty plant or Batman's wily nemesis, you probably know to stay away from anything by the name of Poison Ivy. In today's Skincast episode, hosts Luke Johnson, MD and Michelle Tarbox, MD explain why our skin reacts to poison ivy and poison oak, how to treat the rashes they cause, and what other types of plants you'll want to steer clear of (*cough* Giant Hogweed *cough*).


Dr. Tarbox: Hello and welcome to "Skincast," the podcast for people who want to learn how to take the very best care of the skin they're in. I'm Dr. Michelle Tarbox, a dermatologist and dermatopathologist at Texas Tech University Health Sciences Center in beautiful sunny Lubbock, Texas. And joining me is . . .

Dr. Johnson: Hey, everybody. This is Dr. Luke Johnson. I'm a pediatric dermatologist and a general dermatologist with the University of Utah in Salt Lake City.

Dr. Tarbox: So today we're going to talk about something you hopefully don't run into personally, poison ivy.

Dr. Johnson: That's right. Poison Ivy is the alter ego taken by Dr. Pamela Lillian Isley, an eco terrorist and prominent enemy of Batman who first appeared in Batman #181. Just kidding. This is a dermatology podcast, so we're going to talk about the plant.

Dr. Tarbox: But great nerd culture. I'm proud of you.

Dr. Johnson: Thanks. So the rash that you get from poison ivy is technically allergic contact dermatitis, or ACD. You can get allergic contact dermatitis to all kinds of stuff. Think of something, you can get allergic contact dermatitis to that thing. But today, we're just going to talk about the plant types of allergic contact dermatitis: poison ivy, poison oak, and poison sumac.

Dr. Tarbox: So the poison plants all have the ability to produce a significant rash in humans upon contact. The first one we're talking about, of course, is poison ivy, because it's sort of the leader of the pack, if you will, of the itchy gang.

So Toxicodendron is its actual name. It's such a nasty plant it has toxic right there in the title. This plant is found everywhere in the United States, except for Alaska and Hawaii. Even in places where it was less common, it's starting to have territory expansions.

And it can really be just about anywhere, because it sometimes gets accidentally shipped with nursery plants around the base of a tree or shrub that's taken from one part of the country to be grown in another part of the country. So you can actually run into it pretty well in most places. Do they have it in Utah, Luke?

Dr. Johnson: They do. It shows up just about everywhere in Utah. How about in Texas?

Dr. Tarbox: Not as much in the part where I live because it's very dry and that plant likes a lot of moisture. But when we have our wet years, we end up with some expansions of the growth of those things out from around the bases of the nursery plants. And it's out in the countryside most places in the country.

Dr. Johnson: "Leaves of three, let it be." That's the saying, because this plant has what they call compound leaves with three leaflets. So a little plant stem will actually have three little leaves coming out of it, and the middle leaf is kind of longer than the others.

When I was learning dermatology, I remember complaining that, "Man, I'm already a doctor, and now they want me to be a botanist? And I'm also supposed to learn about bugs and be an entomologist and all that stuff?"

There are pictures of these plants. We can talk about what they look like. The edges of the leaves can be smooth or toothed. The surface can be glossy or dull. But I discovered that there are now apps that can identify plants. So instead of trying to memorize pictures or torturing our dermatology residents, we should probably just use these apps.

So some that I found are PlantSnap, Leafsnap, and Planta. So if you're going to go out hiking or camping, especially if it's somewhere kind of new for you, you might want to download one of those apps first and make sure that your children aren't tromping around at a big poison ivy patch.

Dr. Tarbox: I like that plan. One of the things that we kind of can unify with these plants is that they all have an oil that they make that is the problem child, the thing that causes the rash. And so that makes the rashes look a little kind of shiny or glossy, a lot of the time but not all of the time.

Dr. Johnson: They only produce this stuff at certain times of the year, certain seasons, or when the plants are doing whatever plant things they do. But sometimes these little black dots show up and that's the urushiol.

Poison oak and poison sumac also exist and are kind of similar. Poison oak is found in western North America and the Southeastern US. It's not a tree, despite the fact that oak is in the name. That was surprising to me. It's more like a shrub or a vine. And it kind of similarly to poison ivy has the three leaflets, and in the spring it has white flowers. So if you find something in the spring that has red flowers, you're probably good.

Dr. Tarbox: Yeah, white flowers, that could be a problem. Could you imagine if somebody made a bouquet out of those and then just . . .? Their poor little hands.

Poison sumac is also a thing. Less common. It is a shrub or a small tree up to about 30 feet and it tends to grow in wooded swampy areas like Florida in the southeastern portion of the United States. It's also present in wet, wooded areas in the Northern United States. So you and I probably don't have a lot of sumac in our areas, Luke.

Dr. Johnson: I don't think so. So they're easy to avoid, which is what you should do for all of these if you can. Just don't come into contact with them. Stay in your house, play video games, everybody will be fine. Well, probably not. Actually, there are some dermatologic conditions that can be associated with excessive video game playing.

So if you do come into contact with a plant, well, you want to wash the affected area. Not necessarily with just normal soap either. You want to use laundry soap, dish detergent, rubbing alcohol, and rinse. You want to get that plant juices out of anywhere that it could have gone, so rinse onto your nails. And remember, it could have gotten on your clothes, so carefully remove your clothes, perhaps with gloves or something, and put them in the wash.

Dr. Tarbox: And you want to wash your whole body surface because we may touch parts of our body with our hands that made contact with oil and transfer it. So one almost emergency situation that more commonly affects men is when they have contact with the plant and then maybe they go to the bathroom. And you can imagine that the severe allergic contact dermatitis on that part of your body might be significantly uncomfortable.

There are products that are made specifically to help you to remove the oil that causes the rash. One of the most common ones you can find is called Ivy Block. Again, we have no relationship with any commercial product. We just like people to be able to find the product in the stores.

So the active ingredient in Ivy Block is something called bentoquatam, and it tends to protect the skin like a shield against the poison ivy, poison sumac, poison oak by kind of blocking skin contact with their resin. They also make a soap that can help you to rinse off the oil very well.

Any of these preventative products, of course, you wouldn't want to get in your eyes. You obviously don't want to get poison ivy residue in your eyes either.

And one very important thing is to not try to go all vengeance on the plant and burn it. I've had several patients who actually, after they determined what had caused their rash was poison ivy, then sort of in retribution ripped the plant out of the ground and burned it. The problem is if you burn it, then you aerosolize the oil and you can actually give yourself a chemical pneumonitis. You can give yourself poison ivy in your lungs if you burn this stuff, so you should never burn it.

If you think you've been exposed to airborne, poison ivy resin from burning that kind of thing, you may need to seek medical care. So do not burn anything you think is poison ivy.

Dr. Johnson: "Leaves of three, let it be." Do not incinerate.

Dr. Tarbox: Now what about the rash, Luke? Does everyone who touches poison ivy get a rash?

Dr. Johnson: Interestingly, no. Maybe only about half of people seem to actually get this allergic contact dermatitis to poison ivy. And like other allergies, if you've already been exposed in the past, that means your immune system is extra ticked off if it sees it again. So if you've had a poison ivy rash in the past, and you get exposed to poison ivy again, you'll probably get a rash within a few hours of touching the plant.

However, if you've never seen poison ivy before . . . well, if you have not ever touched poison ivy before, and you end up touching it, then the rash might take a couple of weeks to show up. So remember how you were hiking in the woods two weeks ago? Do you have a rash now? Maybe it was poison ivy.

And it occurs where the leaves brush against the skin. So sometimes dermatologists refer to something looking like an "outside job." So if we're having an immune reaction within our body against something that's going on in our body, not a reaction to something outside our body, it usually doesn't show up as nice lines or swirls or curves and things like that. So if it looks like someplace where a leaf may have brushed and left a rash there, well, it could have been something like this.

Dr. Tarbox: So what do you say we should do if patients get this? How do we take care of it?

Dr. Johnson: Well, if it's not too bad, you can just treat it with over-the-counter stuff like soothing lotions and things and mild steroid creams and steroid ointments like hydrocortisone. A dermatologist or another doctor can prescribe you stronger medicines if necessary.

For really bad poison ivy, especially these people who burn poison ivy, we can sometimes even do steroids by mouth to help get over the reaction because it can be really, really horrible and it can last two or three weeks.

Dr. Tarbox: It can be quite awful. So the really best thing to do is just avoid it. If you, of course, know what the plant looks like, that helps. I encourage people to kind of refresh their memory about what these plants look like before they go on a hiking or camping trip.

You can also wear clothing that will protect the skin from both the sun and from the brush of those leaves. So a lot of sun-protective clothing with long sleeves or long pant legs can be preventative in terms of preventing skin contact. And then you can wear the Ivy Block when you're out and about in areas where the plant might live.

Dr. Johnson: The rash can blister, by the way. So if you see that you've got a blistering rash, it still could be poison ivy.

That's most of the poison ivy/oak/sumac stuff I wanted to talk about. I want to talk about Mr. Freeze next.

Dr. Tarbox: Okay.

Dr. Johnson: Thanks. Was waiting for that.

You can get allergic contact dermatitis to other types of plants as well. Compositae is a super common type of plant that causes allergic contact dermatitis. It doesn't cause it in nearly as many people as poison ivy does, which I guess is why it's not called poison sunflowers. They're just called sunflowers. But there are all kinds of plants in this family, sunflowers and things that kind of look like sunflowers with that kind of circle/radiate/Starburst appearance. It's a common thing we see in dermatology. Tulips can do it too.

Dr. Tarbox: Alstroemeria.

Dr. Johnson: What's that?

Dr. Tarbox: Alstroemeria. So there's a kind of Peruvian Lily that is used very frequently in floral bouquets because it's a hardy plant, and it lasts for a long time and has really beautiful blooms. So the Peruvian Lily or Alstroemeria can also cause contact dermatitis.

Dr. Johnson: So we like plants, but they might not always be your friends. In addition to allergic contact dermatitis, there's also irritant contact dermatitis. So the difference is that to have allergic contact dermatitis, your particular immune system has to be angry for some reason, whereas in irritant contact dermatitis you're coming into contact with something that is just irritating to human skin. A chemical burn is a good example of an irritant contact dermatitis.

And some plants can do it too, including plants that we eat, like garlic. So sometimes especially people who prepare a lot of food with these plants can start to get irritation of their fingertips, for example.

And also, there's this funny condition that some plants can cause called phytophotodermatitis. It's one of my favorites. There are particular plants that have a chemical in their juices and when the juice gets on the skin and then sunlight shines on the juice, you get this big reaction and it can kind of look almost similar to poison ivy. And its significant forms can be this itchy blistery rash. That calms down pretty quickly, but then you're left with this pink-brown discoloration that can last for like two years.

So common plants that can do that are citrus plants like limes. So some people refer to margarita hands. If you were on vacation in Mexico smashing limes for margaritas, you were probably hanging out in the sun too and bam, margarita hands.

There are also different weeds and things, like hogweed, that can do it. So sometimes we'll see this in people who are doing yard work or something.

Dr. Tarbox: And there are also plants that cross-react with a person's allergy to poison ivy. So for some people, it'll be mango peel. If you have a significant poison ivy response, then making significant contact with the peel of a mango fruit can potentially cause you allergic contact dermatitis.

So if you're one of those people who likes to get every last bit of mango out of the mango slice, and your skin is coming in contact with that mango peel, if you've had a reaction to poison ivy in the past, you may get a rash from that. So it's probably safer to just cut the peel off.

Patients can also react to ginkgo leaves or potentially cashew plants if they've reacted previously to poison ivy.

Dr. Johnson: That's all for today. Thanks for hanging out with us, guys. And thanks to our institutions. Thanks to the University of Utah for supporting the podcast, and thanks to Texas Tech for lending us Michelle.

If you like to nerd out about dermatology, you might be interested in our other podcast as well. It's called "Dermasphere." We say it is the podcast by dermatologists for dermatologists and for the dermatologically curious. We talk about dermatosis you can get from video game playing, for example. And I think we've even talked about Super Villains at one point, like they're depicted as having less hair than heroes. So we talk about some fun stuff. You can find that in Apple Podcasts or wherever you get your podcasts.

"Skincast" episodes you can also find on Apple Podcasts or wherever you get your podcasts, and, in two weeks, right in your earbuds. We'll see you then.