Now at peak growth, Alaska’s cow parsnip can cause serious skin burns when activated by the sun

It’s peak season for Alaska’s cow parsnip, those tall, fleshy plants with broad leaves, topped with a crown of white flowers.

Known officially as Heracleum Maximum and more commonly as pushki, cow parsnip can be a problem for people who get its sap on their skin, especially on a sunny day. That’s because the sap contains what are called furocoumarins that are sensitive to ultraviolet light and can cause painful blisters and rashes.

And despite traditional uses of cow parsnip for food and medicine, Matt Bowser, a biologist with the Kenai National Wildlife Refuge, says it’s the number one poisonous plant he warns people about. As Bowser puts it, a person does not need to go looking for trouble with cow parsnip.

Listen:

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This interview has been lightly edited for length and clarity.

Matt Bowser: So the way it works is these furocoumarins, they will kind of get stuck in your DNA. So if you think of your DNA strands, think of it as a ladder, it’s the picture you often see. Well, these furocoumarins fit just right, as if they’re kind of extra rungs. They’ll pop in to your DNA. And … so it gets into your skin, this is what happens, it will get into your DNA, they’ll pop in, these chemicals will pop into your DNA, and now also pop out, and eventually your body will flush them out, flush them out through your urine. So there’ll be pretty much harmless.

But in the presence of UVA light, if those chemicals are sitting in, still sitting in your DNA at that time, they’ll get excited, and they’ll bind to your DNA. And it’s like having extra rungs on that ladder now that won’t let go. They’re stuck in your DNA. And then at that point that DNA is done. It’s no longer useful to the cell. It can’t be used to be unzipped for making proteins to be read and make proteins or for the cell to divide. So basically, those cells are now going to die very soon. And that’s why you don’t feel it right away whenever you get exposed to cow parsnip. It takes a while for that cell damage to start to take effect.

Casey Grove: Yeah, and how long does it take, if, you know, if it’s in the presence of sunlight? And then what actually happens? I mean, what does it look like?

MB: Generally, not much happens right away, right when you’re exposed to it. But then you’ll usually get kind of an itching or burning, starting to have what looks like a rash. And it’s often not until the next day or so to just start to have a pretty severe, painful rash. And it often blisters with big pouches of pus, and then eventually those will rupture. And it takes quite a while. It can take weeks to heal. It looks a lot like you’ve had a severe burn.

CG: Do you know if certain people are more sensitive to it than others? I mean, I’ve heard stories like that, but I haven’t, you know, read any actual information, you know, research that says that.

MB: I don’t think so, because this is not like poison ivy. That’s a kind of allergic response. This is not an immune response, it’s just a matter of whether you get it into your skin, if you can get the sap into your skin, and then have your skin exposed to light. It’s just a matter of if you get it on your skin and there’s enough. I’m sure the plant varies in time, too, so individual plants, and throughout the season, I imagine the amount of your occurrence in the tissues would vary. So I think that’s more of what’s going on, or just luck of the draw, how much you get on yourself and how sunny it was. I think that’s more what’s going and not differences in how individual people react.

CG: Yeah, and I mean, it seems like this time of year, in a lot of parts of Alaska that have cow parsnip, they’re huge. They’re like, six, seven feet tall, maybe taller. So maybe this is kind of like the time of the year that they’re at full force, and they’re just bigger, you’re gonna run into a more and they have maybe more of that chemical on them. Does that sound right?

MB: Yeah, I think we’re just at the time of year where they’re at their maximum growth right now. That’s really what it is. So they’re trails that might have been cleared in the spring, these things have have grown up, and people are just pushing past on breaking them and exposing themselves to the sap. That’s, I think, that’s what’s going on.

CG: So in your work with the Kenai National Wildlife Refuge, I imagine you’re out in this stuff fairly often. And I understand too, that you try to warn your coworkers about it, right?

MB: That’s right.

CG: What do you say to them about avoiding cow parsnip?

MB: Sure, yeah, I give a poisonous or dangerous plants talk in the spring to all of our seasonals, and this is the the number one plant that I show them. All the other plants that are out there, you know, Devil’s club, for example, it’s a lot friendlier. IT might be pokey, but you’ll you’ll learn about that on your own, no problem. We’ll figure out that that’s not much fun to walk through a bunch of Devil’s club. And then the other plants, you kind of have to ask for trouble. If you start eating some of our really poisonous plants, then you shouldn’t be harvesting plants unless you know what you’re doing.

But cow parsnip is different where you do not have to be looking for trouble. You can just be out and about minding your own business and brush up against a damaged cow parsnip and then you’ve got yourself a severe reaction. So that’s the number one plant that I teach, I want people to recognize and know to avoid.

Well, I wear leather gloves and long sleeves whenever I’m in the field, especially if I’m gonna be pushing through. that works great for Devil’s club and cow parsnip to protect you. So I’ve only ever had an issue once with cow parsnip, and that was small. It was on my own time. Being careful and and dressing appropriately really, really helps. And then when I am pushing through it, I’m trying not to break. it I’m just gently pushing past the plant. If it hasn’t been damaged, you should not get exposed to this sap. It’s not just touching it that’s causing the problem. You have to get the plants juices onto your skin.