Info You Should Know: Poison Ivy

by Mary Dysart – Ohio Chapter Volunteer

It’s spring and time for trail maintenance, foliage clearance, and general yard work. Lurking along the trunks of trees, hiding near the bushes and along the trail, is Poison Ivy. An encounter with poison ivy can leave you feeling miserable for weeks.

Although animals can experience exposure to poison ivy and suffer no ill effects from its oil clinging to their fur or skin, humans don’t have it so lucky. Make note: if you rolled in a poison ivy bush, the results would most likely be disastrous – and dangerous!

Poison ivy was named by Captain John Smith in 1609. First published records describing poison ivy date back to the 1600s. So, early settlers and Native Americans suffered from allergic reactions just as we do today.

What is Poison Ivy?

Poison ivy (Toxicodendron radicans or Rhus radicans) is widespread throughout North America, growing from Canada to the southern United States. A member of the cashew family, Anacardiaceae, it is the most widespread of a group of related species including poison oak and poison sumac. These plants contain the highly allergenic urushiol, which causes the painful symptoms of itching, burning, and blistering on affected skin.

There are two varieties: vine and shrub, depending on its geographic location. Trailing or climbing vines are typically found in eastern North America, while in western areas it is a low, bushy shrub. Both varieties have three-parted, shiny pointed leaves that can have smooth, toothed, or lobed edges. Small, inconspicuous flowers with whitish berries hang in clusters beneath the leaves.

All parts of the poison ivy plant – roots, stems, leaves, flowers, and berries - are potential irritants. The tiniest bruise on a leaf is enough to unleash the urushiol oil, which is contained in all parts of the plant.

There is little hope of avoiding contact with poison ivy. This stubborn and adaptable plant grows just about anywhere it takes root. Its vines climb trees both in rural and urban areas. Be careful, the vines can branch out two or three feet, blending with the tree, making it more likely that you’ll come in contact with it. Keep watch in floodplains, along lakeshores and stream banks, and in fields and wooded areas. Be diligent as you walk on the edge of a road or a forest – poison ivy is usually lurking there. When developers disrupt a previously stable land area by building malls or housing subdivisions – poison ivy appears on the edges or in the yards of new homes.

What causes the rash?

The cause of our rash-induced misery is urushiol, the highly irritating oil contained in each poison ivy plant. Derived from urushi, the Japanese name for lacquer, it was applied on the gold leaf on the golden temple in Kyoto to protect it not only from the elements, but also from thieves. One touch of the oil would cause a rash and lead authorities to the "red-handed" thief.

Urushiol flows within canals in the leaves, stems, roots and skin of the berries, making the entire plant a potential allergen. Harmless as long as it stays within the plant, urushiol has an uncanny ability to escape and land on your skin or clothing. Any disturbance, such as an insect biting a leaf or a human hand brushing against the plant, will release the oil.

It only takes one nanogram (billionth of a gram) of urushiol to cause a reaction. Typical contact with poison ivy results in 100 nanograms of urushiol getting on your clothing or skin.

This makes clearing away the offending plant, especially during spring when sap is rising, a potentially "scratchy" situation. It’s better to wait until the winter months. Urushiol is still present in the stems and roots of the dormant plant, just not as potent.

Urushiol is the ultimate natural hitchhiker, riding on the fur of animals, such as cats or dogs. Pat a dog’s head after it romps in a field with poison ivy and the oil may be passed on to you. Urushiol attaches to clothing and can rub off on car seats, furniture, or anything you sit or lean against. Urushiol also travels through air when it is carried in smoke or soot from burning poison ivy vines, brush or your firewood. Inhaling this smoke as it burns is the most dangerous method of contracting the allergen.

How do I know I have Poison Ivy?

You’ll know when you have an allergic reaction to poison ivy! Symptoms include itching, burning, and redness in the affected areas of your skin. Within a few hours or as long as five days after contact, you will develop small blisters. As time passes, the reaction can become severe dermatitis, with larger blisters, swelling, headache, and fever. Symptoms depend on the severity of the allergic reaction. Inhaling urushiol from smoke or soot may result in much worse symptoms which could require hospitalization.

Contrary to popular myth, the poison ivy rash is not contagious. Rubbing the rash will not spread it to other parts of your body, unless you still have urushiol on your hands. Breaking the blisters will not release urushiol oil, but can cause infection and increase the likelihood of scarring. If you have excessive amounts of fluid in your blisters, see a doctor for treatment.

What are the best treatments for Poison Ivy?

Once you have the rash, it is simply a matter of time before you heal. The allergic reaction has to run its course, which can be from one to three weeks. If you suspect you’ve come in contact with poison ivy, remove contaminated clothing and keep them separate from other laundry. Wash them thoroughly several times before wearing them again.

Then, wash all affected areas with a strong soap and plenty of water. Apply rubbing alcohol. If you already have blisters, apply antihistamine cream to ease the itching. Do not break blisters! If you have intense itching, or the rash has spread to your face, genitals, or large areas of your upper body, seek medical treatment to ease your symptoms and prevent scarring.

How can I protect myself?

If you love the outdoors, sooner or later you’re going to encounter this ubiquitous plant. Your best defense is to avoid contact completely. When doing trail maintenance or simple yard work, wear gloves, long sleeved shirts and long pants. Keep your pants tucked into your shoes to prevent the oil from getting under your pant legs. Also, do not touch your face while wearing your work gloves. Change your clothing before getting into your car or sitting on any of your furniture. Finally, after potential exposure take a shower as soon as possible.

Remember, even if you’ve never had a reaction, you can develop sensitivity at any age. Poison ivy is everywhere – so be careful out there!

Poison Ivy Facts

¼ ounce of urushiol could cause a rash on every person on earth.
Urushiol oil can remain active on any surface, including dead poison ivy plants, for one to five years
About 90% of the population experiences a reaction to urushiol, with only 10% of the population avoiding the allergy throughout their lifetimes.

Resources:
Common Poisonous Plants and Mushrooms of North America, Nancy J. Turner and Adam F. Szczawinski
Outwitting Poison Ivy, Susan Carol Hauser