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Poison Ivy. Photo by Bet Zimmerman.  

Native Americans believed that dermatitis could be caused by an invisible vapor given off by Poison Ivy. More...

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If you like to use native plants in your garden, how about a hardy perennial sporting shiny foliage that turns a flamboyant color in fall, and fruit that provides a winter food source for warblers, woodpeckers and bluebirds.  In 1783, botanist John Bartram sold just such an ‘ornamental’ plant in his Philadelphia nursery (see Jefferson's Garden).  But about 150 years earlier, Captain John Smith noted that, while this plant looked like English Ivy, “being touched, [it] causeth rednesse, itchynge, and lastly, blisters.” Smith was credited as the first to write about “Poison Ivy.”  Perhaps he accidentally used it as toilet paper (it’s been done).

Poison Ivy. Photo by Bet Zimmernan.
Thomas Jefferson considered Poison Ivy an ornamental. Clusters of three leaflets that alternate on the stem (instead of being directly opposite each other) distinguish it from similar plants.

To help identify it, children learn the mnemonic "leaves of three, let it be; berries white, danger in sight."  The leaves of Poison Ivy (Toxicodendron radicans) are often, but not always, shiny with some notches along the edges.  Clusters of three leaflets that alternate on the stem (instead of being directly opposite each other) distinguish it from similar plants.  It can grow as a vertical woody vine, ground cover, or even a small bush.  This vexatious vegetation is common in disturbed areas like roadsides and pastures.  Vines can root, or it can spread via rhizomes (root-like underground stems) that send up shoots.  It is also disseminated by animals that eat the whitish waxy berries produced by female plants, or via water, since the berries float.

The evil agent in Poison Ivy is urushiol (you-ROO-shee-ol), which leaks out of broken resin ducts.  It is “one of the most potent external toxins we know,” according to Dr. William Epstein, a University of California professor of dermatology.  Epstein estimated that less than one ounce of urushiol would be enough to give every person on the planet a rash.

The severity of the reaction depends on the thickness of the skin that was exposed, how much oil it came into contact with, and the person’s susceptibility.  Dr. Epstein and Vera Byers conducted skin tests, and found that 10-25% of people are non-sensitive to urushiol, but even they can develop an allergic reaction after repeated exposure.  Another 25% are mildly sensitive; 25-30% are moderately sensitive; and 10- 20% are severely sensitive (those who are allergic to cashews, mangos or pistachios may fall into this last category, since Poison Ivy is in the same family).  Some studies indicate that how allergic you are to Poison Ivy may be inherited.

The itchy, oozing red rash often shows up in lines on whatever part of the skin came into direct contact with the oil.  The rash can appear within 8 hours after exposure, and usually lasts 2-3 weeks.  It is not contagious.  Scratching and breaking the blisters does not spread it, but can slow healing and invite infection.  You can get it even if you never leave the house, by touching a pet that brushed against it during its travels.  Urushiol can also remain on unwashed clothing like gloves or garden tools for several years. The toxin is still active on plants that have been dead for years. 

Since urushiol starts to bind with skin within 10 minutes, it is important to get it off immediately.  Rinse with plenty of cold water, Tecnu Skin Cleanser, or rubbing (isopropyl) alcohol.  Be sure to wash clothes and gloves.  Wipe off tools and shoes with rubbing alcohol.  Once you have a rash, I have found that swimming in a lake dries it up; others say a dip in the ocean helps.  Antihistamines like Benadryl and over the counter creams or ointments like Cortaid provide some relief from the itching.  Moderate or severe cases can be treated with prescription corticosteroid pills or injections, which are very effective, especially if the rash involves your face or eyelids.  Severe reactions (in the mouth, trouble breathing, or infected rashes) need immediate medical attention.

The Poison Ivy plant is a tough bugger.  Rhizomes buried deep in ground can even survive fire.  Never burn it, as the heat vaporizes the oil.  If it gets in your lungs, it could be fatal.  Do not mow it with a push mower, hit it with a weed whipper, or pull vines off trees, as that could get the oil all over you.  If you believe in “Better Living through Chemistry,” sever the vine 4-6” above the ground and treat the stump during active growing season with an herbicide for woody plants like Roundup or Brush-B-Gon.  If it re-sprouts, re-treat.  Deer may help control it – they love to browse on it.  I had read that goats like to eat it, but unfortunately our Pygmy goats prefer flowers.

UPDATE: Zanfel 30 Seconds Wash For Poison Ivy Oak And Sumac Rash Cream is getting rave reviews for poison ivy treatment. It binds with the urushiol toxin, deactivating it. Paige Westerfield of Woodstock, who has suffered cases that sent her to the hospital, says it dries the blisters up like magic.


Other interesting Poison Ivy facts:

  • Poison Ivy is common wherever soil has been disturbed – along roads, stonewalls, clear cuts, riverbanks and pastures.  It may be considered an intrusive weed, but does not qualify as “invasive” because it is not introduced.   Thomas Jefferson considered it an ornamental.
  • It can be confused with Virginia Creeper (which usually has 5 leaves in a cluster), Trillium, blackberry, raspberry or strawberries.  To tell it apart, look for groups of three leaves that are not wrinkly on top, and that alternate on the main stem – i.e., are not directly opposite each other.  Unlike blackberry and raspberry, Poison Ivy vines have no thorns.
  • Each year, reactions to poison-ivy are one of the most often cited causes of workers' compensation claims (Ohio Perennial and Biennial Weed Guide)
  • Poison-ivy has been cultivated in gardens and sold as an ornamental in Europe and Australia. (Ohio Perennial and Biennial Weed Guide)
  • In the Netherlands, they plant it on purpose to prevent dike erosion.
  • Native Americans believed that dermatitis could be caused by an invisible vapor given off by Poison Ivy (McNair, 1921)
  • Some people claim that rubbing exposed skin with the common jewelweed (Impatiens capensis) before or immediately after contact may lock it out. A 1997 study by D. Long et al concluded it was ineffective.
  • One product used by outdoor workers is Tecnu Outdoor Poison Oak And Ivy Skin Cleanser (available at places like Walgreens), a lotion which reportedly breaks up the oils even if used within 2-8 hours of exposure. Others rinse with a 10% Clorox mixture followed by a prolonged water rinse. Some sites recommend foaming up (don’t scrub and abrade skin) with alkali soap Fells Naphtha or Ivory Soap that does not contain lanolin (which spreads the oil.) 
  • Wet compresses, and cool baths with Aveeno colloidal oatmeal can ease the itching. 
  • Poison Ivy not all bad.  Historical records indicate that a decoction of Poison Ivy leaves was taken as a tonic and “rejuvenator” by Houma Indians of Lousiana It was used as an emetic by Cherokee, and also to CURE running or non-healing sores by Kiowa (whole or broken leaves were rubbed over boils or skin eruptions.)



Originally published in the Villager newspapers June 8, 2007


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