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The Monday Garden
Fun in the Sun: Poison Ivy

Issue No. 0118 - June 27, 2004
by Sue Sweeney


What would summer be without old-fashion hot dogs, sunburns and poison ivy? All are life-threatening, if you count the chemicals in the hot dog and the carbís in the bun.

picture: Poison ivy flower buds, Hoyt Street Alley Stamford CT May 2004

Did you know that poison ivy is a problem only for humans? Birds, of course, spread the seeds galore. But did you know that the seventh most important Indiana deer food is poison ivy? (How does the USA Forest Service figure this stuff out?). Rabbits like it, too. Bees make great honey from the pollen, which fortunately isnít toxic to humans. Goats, it is said, like poison ivy so much that they are an effective control. Mysteriously, the toxins donít pass into goat milk. And squirrels nest in it.

Do wild critters think of this human-enhanced native species (See Issue 74) as ďhuman-baneĒ?

FAMILY HISTORY: Poison ivy (Toxicodendron radicans) belongs to the family Anacardiaceae (Cashews and Sumacs). The 600 family members are mostly tropical. All are trees, shrubs or woody vines. Many have edible seeds or fruits such as cashews, mangos and pistachios. The family is also known for useful tannic acids, resins, oils, and lacquers (e.g. the Japanese lacquer tree).

Poison ivy itself (which is either one species, along with poison oak, or about 15 Ė the toxicologists donít agree), is native to a good part of the Americas (more eastern and northern but you can get a rash in Mexico City and the Bahamas) and parts of Asia. Early European visitors, astoundingly, took the stuff home because they thought it would look pretty in the autumn garden. It now grows the British Isles, Europe, and Australia.

picture: Poison ivy enjoying the view at Stamford's Cove Island

Picture: Poison ivy on a stone wall, Bedford Street, Hoyt Street Alley, Stamford CT June 2004

HOW IT WORKS: All parts of the poison ivy plant (except the pollen) contain a pale, yellow oil called ďurushiolĒ, after the Japanese word for lacquer. Urushiol is chemically stable so it doesnít break down or evaporate easily; itís sticky so that it readily adheres to anything it touches, and itís not water soluble so itís hard to wash off.

If this werenít enough, urushiol starts to absorb through humans epidermal skin in minutes. It bonds with inner-skin proteins to create new compounds, which the immune system of 80 to 90 % of humankind treats as an invading disease. So the rash, blisters, etc, are all our allergic reaction to the plant. Sort of like a thousand mosquito bites. Like auto-immune diseases, a serious dose of poison ivy can damage joints and internal organs. So if you get a major attack or it affects eyes, lungs, etc., get yourself to the emergency room ASAP.


picture: smooth-edged poison ivy leaf

picture: toothed poison ivy leaf

picture: lobed poison ivy leaf

picture: oak-leaf shaped poison ivy leaf

The chemically-stable oil is always active in the plant, dormancy and death, not withstanding. Century-old lab specimens and unwashed camping gear have caused rashes. Even fire doesnít destroy it. When poison ivy is burned, the urushiol bonds with the soot particles, and happily floats off in the smoke (and into your lungs). Donít ever burn the stuff, and watch out for forest fire smoke.

Just like the grand jury, past immunity is no guarantee of future immunity. Because weíre talking an allergic reaction, the effect is cumulative with repeat exposures. You might get a very mild case the first time but that just your immune system warming up. Also, the reaction will be less if your immune system is suppressed. However, the reaction increases as skin thins with age, and if your natural protective oils are thinned by washing or natural causes. Lastly, the oil is not on the plantís surface until secreted through even the smallest bruise. So if the rabbits were dancing around the patch right before you got hereÖ

Lastly, urushiol not only adheres to anything it touches, and stay on the surface a long time, it transfers readily from surface to surface. Like from the dogís coat to your face. It doesnít take much; urushiol is so potent that they say that a ľ ounce could give the entire human race a rash.

LEARN RECOGNIZE THE PLANT So what to do? Any boy scout (and all girl scouts) can tell you to learn recognize the plant and avoid it. Look for the three leaves and the almost-always present sheen to the leaves. Learn to tell its various leaf forms and colors; If youíre not sure, treat the plant as poison ivy.


reddish new poison ivy leaf light yellow-green poison ivy leaf

dark green poison ivy leaf


pictures: winter and spring views, Stamford CT , 2004


Picture: Poison ivy with seedlings, Hoyt Street Alley, Stamford CT June 2004; the heart-shaped babies are porcelainberry

Eradicate it when possible. You may be able to double-wash your tools, clothes, and the dog, but believe me itís easier to pull up the poison ivy than to wash the cat. If you canít borrow a goat, see Issue 74 on how to get it out of your yard; and Issue '112

on the (sparing) use of herbicides.

Know the first aid. Since urushiol starts absorbing in minutes, get it off fast. Itís not water soluble so using plain water or water with an oil-based soap (e.g must organic products) spreads it like oil on a fire. Use alkali soap like yellow laundry soap or naptha. And take a shower-- not a bath -- or you could end up with a whole-body rash. Alcohol and other solvents will remove the urushiol (rinse with water) but also strip the skinís protective oils so be even more careful about additional contact.


Picture: jewelweed, Bedford Street, Stamford CT June 2004

In the wild, use any available water. To get the oil off, use mud, baking soda, wood ashes or bouncing bet (Saponaria officinales) (a useful European settler, high in saponin, makes an oil-free soap). Whether you can find water, apply jewelweed (Impatiens spp.) juice (suspected to have urushiol-blocking compounds and is a known anti-inflammatory); a plantain (Plantago) leaf poultice is also said to help for similar reasons.

There are over-the-counter products, some developed for the USA Forest Service, said to block the oil from entering the skin and/or to remove it after contact.


picture: poison ivy mixed with woodbine, a native vine with FIVE LEAVES

From The Monday Garden. Copyright © by Sue Sweeney. Reproduced with permission. 

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