Poison Ivy: Leaves of Three, Let it Be

By Jody Kelly – July 1, 2014

This familiar axiom appears on signs posted on the Roy and Ann Butler Hike and Bike Trail around Lady Bird Lake, along with a picture of Toxicodendron radicans, commonly known as poison ivy. Trails in Central Texas provide “the ideal growing environment—part sun and part shade,” according to Susan Rankin, botanist and executive director of The Trail Foundation (TTF).

Despite these posted warnings, many runners, walkers, cyclists, and boaters may not worry much about the plant—until they get home and start scratching. How to treat the itchy rash then becomes a primary concern. Later on, folks will want to know how to prevent the rash from occurring on their next outdoor adventure. And some may want to identify the pesky plant to avoid it or eradicate it from the landscape (if not from the world).


Touching the stems, leaves, and roots of the plants releases a chemical called urushiol. It takes a very small amount of the oil—50 micrograms, less than a grain of salt—for an itchy rash to develop. The oil is easily transferred from one surface to another, so contact with something that has brushed against a plant—camping equipment, a pet, gloves—can provide exposure. It’s also possible to have a reaction from inhaling smoke from burning plants. The allergic reaction to poison ivy is called “delayed hypersensitivity” because the reaction doesn’t occur for some time after exposure, anywhere from hours to days later. In fact, many people don’t have a reaction the first time they encounter poison ivy; additional contact eventually triggers the allergic response, which varies from person to person in severity. Sensitivity to poison ivy can change over the course of a lifetime, so it’s a good idea to pay attention to foliage when enjoying outdoor life in Central Texas.


You may already know if you’re among the 15 percent who aren't allergic or part of the 20 to 30 percent who are highly allergic to poison ivy. That leaves a large group that reacts to the plant in some moderate fashion. In any case, it doesn’t hurt to take poison ivy contact seriously.

After known—or suspected—contact with the plant, it’s important to remove the oil from the skin (this substance causes the reaction, and urushiol can remain on clothing, skin, and fur for a long time). As soon as possible, rinse with water; dousing within the first five minutes of contact is very effective in preventing allergic reaction. Before the first itch, scrub off the oil with a lengthy, soapy shower and shampoo hair. Rankin recommended using Tecnu Poison Ivy Scrub, available without a prescription at many local drugstores, because “it binds with the oils and they can then simply be rinsed off with water.”

Carefully clean everything that might have come in contact with the plant. Toss clothing worn during the outing, as well as any towels and washcloths used for bathing, into the laundry, and clean footwear. If poison ivy was encountered while gardening, scrub all of the tools used—including the lawnmower. If the dog was exposed, give it a good bath as well. These actions may prevent or lessen the effects of the oils.

If the rash develops, there are several home remedies to try; Heather Herrick, a local athlete who has a master’s degree in botany and wetland ecology, suggested the following.

  • Keep the area dry by dabbing it with 60 percent alcohol, if you can stand the sting

  • Cool the affected area with ice in a bag for a few minutes several times a day, drying the area afterwards

  • Apply calamine lotion or hydrocortisone cream in the highest percentage available


If these actions don’t solve the problem, it may be time to get medical help. According to the American Academy of Dermatology, see a doctor or visit the emergency room if these symptoms develop:

  • Trouble breathing or swallowing

  • A rash that covers most of the body

  • Many rashes or blisters develop

  • Swelling occurs, especially if an eyelid swells shut

  • Rash on the face or genitals

  • Fever of more than 100 degrees

  • Much of the skin itches, or nothing seems to ease the itch



Stay in the middle of the trail to avoid contact with greenery. Avoid bushwhacking; you’re more likely to encounter poison ivy when off the beaten path. While working in the garden, wear long sleeves, long pants, a hat, gloves, socks, and old shoes to protect the skin. Make sure clothing and equipment that comes in contact with poison ivy is washed right away.

The City of Austin Parks and Recreation Department, upon request from TTF, cuts back the poison ivy in some areas rather than use herbicides, which would kill a broad range of beneficial native plants and wind up in the lake. Besides, the plants will always come back, Rankin noted.


Plants with leaves of three seem to be everywhere, but some of them aren’t poison ivy. Virginia creeper, which is a pleasant garden plant and turns red in the fall, is often mistaken for poison ivy. On the other hand, a vine with fewer leaves or reddish leaves may not appear to be poison ivy, but it is. During the cooler months, poison ivy becomes dormant and loses its leaves but the bare stems can still cause a rash. Contact with dead poison ivy plants can also result in an allergic reaction.


True or False?

1. Scratching the rash causes poison ivy to spread.

False. Scratching open the blisters can cause an infection, but it doesn’t cause the rash to spread.
If you eat poison ivy, you could die.

2. If you eat poison ivy, you could die.

True. Because allergic reaction would occur in the digestive tract and airways, ingesting poison ivy could be fatal.

3. Urushiol oil can remain active on surfaces for as long as five years.

True. Even dead poison ivy plants can retain urushiol oil for this length of time.

4. Poison ivy only grows on the ground.

False. Poison ivy can be found as a climbing vine, growing in trees.

5. Poison oak and poison ivy are the same plant.

False. While they both contain the chemical urushiol, poison oak (Toxicodendron diversilobum) is shrubby; its leaves are a lighter green on one side and look like oak leaves.

Next Article

Related Articles


Up Your Health & Fitness Game

Stories from the community and the latest on health, nutrition, fitness and wellness.
  • Austin Fit Magazine
    Be the Starfish Thrower
  • Article title
  • Austin Fit Magazine
    Looking Ahead to Spring 2021: ...
  • Article title
  • Austin Fit Magazine
    Mental Health Column: How to Find a Great Therapis...
  • Article title