Texas Parks & Wildlife Magazine   


Oct 2011 cover image hunting

Poison Ivy Primer

How to avoid this frightening flora, or at least lessen the agony of exposure.

By Sheryl Smith-Rodgers

Not long ago, the undersides of my forearms itched. I paid little notice. By next morning, the areas had morphed into a rash. I shrugged it off. Day three, though, when my increasingly itchy dots erupted into bumpy red patches and some began to ooze, the proverbial light bulb went off — duh, I had poison ivy!

Like 85 percent of the population, I’m allergic to the noxious plants. Even if I were among the lucky few who say they’re not, that could change. According to dermatology studies, immunity can weaken with repeated exposures. Either way, here’s my simple advice: Learn to recognize the three poison ivy species and stay away from them!

Toxic oil

All parts (except the flowers, pollen and fruit pulp) of poison ivy, poison oak and poison sumac contain urushiol, an oily substance that triggers dermatitis, but only in humans. Birds and animals that eat the berries and hang out in the wretched stuff aren’t bothered by it.

Urushiol’s tricky, though. Years ago, I held my then-toddler-aged son in the crook of my arm. Several days later, I itched with poison ivy. Unbeknownst to me, Patrick had sat in the plants. Urushiol adheres to nearly everything, including clothing, tools, shoes, animal fur and even smoke particles.

Warning: Never burn poison ivy! If you’ve been exposed to and inhaled infected smoke, get to an emergency room fast.


Time matters. Allergic skin reactions start eight to 48 hours after contact. Right away, wash the area with lots of tepid (not hot) water. As soon as possible, wipe affected areas with rubbing alcohol to neutralize and leach urushiol from the skin (plain soap and water won’t work). Then take a long shower. If you wait too long to wash the poison ivy off, it’s probable that urushiol has bonded with your skin. Prepare to be miserable. (Hikers and campers, take note: carry alcohol in case of exposure.)


See a doctor if you have a severe reaction or a rash breaks out on your face or genitals. Prescription corticosteroids by pill or injection will stop allergic reactions. For milder cases, relieve the itch with topical creams containing cortisone. Apply calamine lotion (not Caladryl) to help dry up oozing blisters. Contrary to popular belief, that fluid doesn’t spread the rash.

Hot showers draw out histamines from the skin and provide temporary relief, not to mention a little ecstasy (ask anyone who’s had poison ivy). Just be careful not to burn your skin! Don’t worry — rashes heal and disappear within two weeks. I know firsthand!

Learn lots more about the “toxic trio” in A Field Guide to Poison Ivy, Poison Oak and Poison Sumac: Prevention and Remedies by Susan Carol Hauser.

Identifying the ‘toxic trio’

Poison ivy’s sneaky. Sure, the old adage of “leaves of three, leave them be” may keep most itch-free. But the three species aren’t always that easy to identify.

Poison ivy (Toxicodendron radicans)

Three leaflets on one stem have smooth, wavy or serrated edges. They’re shiny green in spring and summer, turning bright red in the fall. Yellowish-white flower clusters produce waxy, white berries. Has aerial roots. Grows like a groundcover, vine or shrub.

Poison ivy may be confused with Virginia creeper (Parthenocissus quinquefolia), box elder (Acer negundo), peppervine (Ampelopsis arborea) or cow itch vine (Cissus trifoliata). 

Poison oak (Toxicodendron pubescens)

Three leaflets are more often lobed and resemble white or red oak leaves. Smooth, green berries turn hairy and white. Grows like a low shrub. 

Poison sumac (Toxicodendron vernix)

This poisonous tree prefers swampy areas and can grow up to 25 feet tall. One leaf consists of seven to 13 leaflets, arranged in pairs with a single leaflet at tip. White berries distinguish this species from beneficial sumacs, which have red berries. Not as common as T. radicans or T. pubescens.


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