I'd feel terrible if I sent you out hiking or running on the trails and didn't warn you about the cow parsnip. This time of year, it's not that big a problem, because the plants are still small, but as the summer progresses, the plants start growing and taking over the trails and fields. Remember, all that midnight sun contributes to explosive plant growth. You'll know the cow parsnip by its big white flowers and by mid-summer, tthis plant can be anywhere from 5 to 9 feet tall. Mention cow parsnip to anyone who has lived in Alaska, and they'll always say, "Yeah, I heard it's edible," but you'll have to go a long way to find someone who has actually eaten it and knows what it tastes like. Check out the video below for one hiker's response. But keep reading. The flowers are beautiful and if you've spent any time in your garden, vaguely familiar. Heracleum lanatum is a member of the Apiaceae family--otherwise known as the carrot family. But remember, this beautiful plant has one big problem. What's the problem? Furanocoumarin--a toxic compound developed by the cow parsnip as part of its chemical defense system against the webworm. Furanocoumarins are compounds called psoralens found in other plants--celery, lime oil--and are thought to be part of the plant's defense system against fungi. It's a great system, but when this compound comes into contact with your skin, and is then exposed to sunlight--the trouble starts. So if you're a celery picker or a bar tender, you too stand a good chance of getting these blisters on your hands.

The reaction time depends on the amount and type of ultraviolet exposure: ultraviolet rays--15 minutes; UVA: between 30 to 120 minutes. But if you're a hiker on Alaska trails, you need to be aware that the clinical presentation ranges from gigantic blisters to areas of hyperpigmentation that can last for weeks.

So what can you do? Avoid contact with cow parsnip. I try hard not to brush up against it, and then I almost always wear long pants and long sleeves when I hike, to avoid being bitten by all those pesky mosquitos. Remember, this is a two step process: 1) you come into contact with the plant and get the chemical on your skin, and 2) you expose your skin to sunlight.

What happens if you're out, you get the blisters and you realize that the field you were hiking through was full of cow parsnip? It depends on how bad your symptoms are--you might try treating the symptoms yourself, or you might need to see a doctor (if you're not from the Peninsula, this most likely means a trip to the Emergency Department) to get treated with steroids. There are prescription (I think) drugs that might help with the hyperpigmentation.

I checked with Skip and in the 40 years he has lived in Alaska, he has never had a problem with cow parsnip, even when walking through fields of it. I can vouch for the full body cover-up as prevention, having hiked for years in Alaska with only blisters on my feet from hiking boots. Here's hoping that you're just as lucky!

The Electronic Textbook of Dermatology has a nice section about phytodermatitis:

http://www.telemedicine.org/botanica/bot5.htm