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How to Identify, Avoid, and Treat Poison Ivy

Don't let a run-in with this pesky plant ruin your summer hiking plans. Learn how to treat poison ivy exposure and avoid it altogether, and brush up on the science behind the backcountry's least-loved vine.

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Once it’s happened to you, you never forget it: You’re hiking when you brush up against a patch of poison ivy. A few days later, your body is covered in an angry, itchy red rash, dotted with painful blisters. You can treat it with creams and antihistamines, but that burning sensation doesn’t go away quickly. The best way to deal with poison ivy: never let it touch you in the first place. Get equipped to beat the burn with our expert advice.

What is Poison Ivy and Where Will I Find it?

What we call poison ivy is actually two different, but related, plants. Which one you’re familiar with probably depends on where you hike. Eastern poison ivy, or Toxicodendron radicans, grows primarily in the eastern half of the United States, and can take the form of either a shrub or a vine. It has even been known to take over dead trunks to form a kind of poison ivy psuedo-tree, an image that’s sure to etch itself into any sufferer’s nightmares.

Westerners are more likely to be familiar with western poison ivy, Toxicodendron rydbergii. It takes the form of a low shrub, and, despite the name, grows in the east as well, though in lower quantities than its relative, with which it sometimes interbreeds.

Poison ivy of one kind or another exists in 47 states. Alaska and Hawaii, you’re in luck, as is California (though another irritating relative, poison oak, is common there).

Why Does Poison Ivy Cause a Rash?

Poison ivy actually isn’t toxic—at least not in the strictest sense of the word. Instead, the itchy rash and blisters that hikers get when they touch it is a kind of allergic reaction. The culprit: an oil called urushiol that’s found in the plant’s stem, leaves, and other parts. When you come into contact with poison ivy, the urushiol binds to proteins in your skin. That triggers an allergic reaction from your body—swelling, itching, and that rash.

Around 15% of people are not allergic to urushiol. Those lucky individuals can hike through poison ivy all day with few to no consequences. The remaining 85% will notice some kind of immune response to poison ivy, with about 25% suffering a severe reaction to the plant.

Identifying and treating poison ivy
Poison ivy’s leaves can take many different shapes, from smooth to notched—a fact that can make it tough to identify from lookalike species without a lot of practice.F.D. Richards

How to Identify Poison Ivy

You’ve heard the old saying: “Leaves of three, let it be.” That’s a pretty good rule of thumb for identifying poison ivy: While the plant’s leaf shape varies and it can either grow as a shrub or wind its way up trees, its leaf arrangement doesn’t change. Look for stems with one larger leaf on the end, and two slightly smaller leaves flanking it. Other characteristics of poison ivy include:

  • Leaves that are reddish-brown in spring, turning to green in the summer, then changing color to a yellow or orange in the fall before dropping off
  • Sprays of small white flowers
  • Heavy clusters of green berries, turning white with a waxy texture as fall approaches.
  • Often grows in disturbed areas or sunny patches of ground.

In addition, a number of benign plants are lookalikes for poison ivy, including Virginia creeper (look for clusters of five leaves and dark blue berries); box elder (check out the arrangement of the leaves, which grow opposite each other rather than alternating along the stem; and wild raspberry (will have thorns on the stem).

How to Avoid Poison Ivy

Since there’s no cure for poison ivy allergy, prevention is key. If you’re heading to an area where you know there’s poison ivy, or you’re planning on bushwhacking, wear long pants, and long sleeves if necessary. Carry a poison ivy wash like Tecnu Original Outdoor Skin Cleanser ($26) and use it immediately if you suspect you touched the plant: Urushiol begins to bind to human skin in as little as 10 minutes, and once that’s happened, it’s impossible to wash off. Once you’re home, scrub any exposed skin with soap and warm water. Even if a few hours have passed, you’ll still be able to get some of the allergy-producing chemicals off of your skin. Then, throw your clothes in the washing machine—poison ivy’s oils can cause an allergic reaction after weeks, or even longer.

Can Dogs Have a Reaction to Poison Ivy?

Your four-legged buddy doesn’t have much to worry about: Besides humans and other primates, relatively few animals have proven to have serious sensitivity to poison ivy. In fact, some species of birds, such as warblers, bluebirds, and robins, eat the plant’s berries. In addition, dogs’ thick fur coats usually keep the urushiol from reaching skin.

However, the oils from poison ivy can stick to your pet, rubbing off on you the next time you reach over to give Fido a backrub. Keep your dog on a leash or on the trail, and give him a bath if you notice him taking a jaunt through any suspect plants. If you’re camping, consider giving him his own sleeping bag or blanket instead of sharing yours.

Need more tips for managing your dog’s health? Check out our guide to performing first aid on your pup.

Identifying and avoiding poison ivy
It’s still possible to get a rash from poison ivy in winter—but because the plants drop their leaves, they’re a lot harder to spot.Nicholas A. Tonelli

How to Treat Poison Ivy Rash

Once you notice those first red streaks appearing on your skin, it’s too late to stop poison ivy rash from happening. Instead, focus on treating the symptoms. Use an over-the-counter corticosteroid cream, calamine lotion, or an antihistamine like Benadryl to manage the itch. If that’s not enough, oatmeal baths help some victims soothe their skin. Folk remedies, like rubbing jewelweed on the affected area, have demonstrated mixed success in studies.

If you’ve tried everything and you just can’t take the itch—or if the rash appears around your eyes, in and around your mouth, or in other sensitive areas—it’s time to seek professional help. Your doctor will likely prescribe an oral steroid to help lessen the inflammation. Whatever you do, patience is key: a rash from poison ivy can last from 1 to 3 weeks.

Can You Die from Poison Ivy?

Death by poison ivy is rare, but it is possible. When the plant is burned (usually as a hitchiker on wood in a campfire), the urushiol in the plant ends up in the smoke. Inhale that, and you could be in for some severe respiratory complications. If you find that you have trouble breathing after making a campfire, seek emergency medical attention.

If I Eat Poison Ivy, Will I Build Up Immunity to It?

Most of us would instinctively shudder at the thought of putting poison ivy in our mouths, and for good reason. The plant can do the same damage to the mucous membranes on the inside of your mouth that it does to the rest of your skin. There’s also no evidence that it works: A 1987 study in the Archives of Dermatology didn’t find any benefit from ingesting the chemicals in the plant.

Unlike most toxins, poison ivy causes its reaction by triggering the body’s immune system. Unfortunately, that means that the more you’re exposed to the plant, the worse your symptoms get. Think of it as a vaccine: Exposure to urushiol teaches your body to more “effectively” fight it off the next time it encounters the chemical, leading to an even bigger (and itchier) breakout.

Climate Change is Making Poison Ivy Worse

In case you needed another reason to worry about our warming world, recent studies suggest that higher carbon dioxide levels are making poison ivy both more common and more irritating. In an experiment at Duke University, researchers found that providing poison ivy plants with additional CO2 increased their numbers by 150%. In addition, those plants also produced more urushiol. The team theorized that the increased number of vines could eventually have a negative impact on forests by out-competing juvenile trees, which is as good a reason for any hiker to go green as we’ve seen so far.

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