Approximately 85 percent of the population will develop an allergic reaction if exposed to poison ivy, oak or sumac.
The cause of the rash, blisters, and infamous itch is urushiol (pronounced oo-roo-shee-ohl), a chemical in the sap of poison ivy, oak and sumac plants. Because urushiol is inside the plant, brushing against an intact plant will not cause a reaction.
Poison ivy, oak and sumac are most dangerous in the spring and summer, when there is plenty of sap, the urushiol content is high, and the plants are easily bruised. However, the danger doesn't disappear over the winter. Dormant plants can still cause reactions, and cases have been reported in people who used the twigs of the plant for firewood or the vines for Christmas wreaths. Even dead poison ivy or poison oak plants can cause a reaction, because urushiol remains active for several years after the plant dies.
Poison ivy is bad news for your yard. The two herbicides most commonly used for poison ivy - Roundup and Ortho Poison Ivy Killer - will kill other plants as well. It’s possible to spray the poison ivy without killing other plants if you pull the poison ivy vines away from the desirable plants and wipe the ivy foliage with the herbicide, or use a shield on the sprayer to direct the chemical.
If you don't want to use chemicals, manual removal will get rid of poison ivy or oak if you're diligent, but you must get every bit of the plant - leaves, vines, and roots - or it will sprout again.
Tip: Never burn the plants. The urushiol can spread in the smoke and cause serious lung irritation.
Whenever you're going to be around poison ivy, oak or sumac, for example trying to clear it from your yard or hiking in the woods, you should wear long pants and long sleeves and, if possible, gloves and boots.
Tip: Wear plastic gloves over cotton gloves when pulling out poison ivy or oak. Plastic alone isn't enough because the plastic often rips, and cotton alone won't work because after a while the urushiol will soak through.
Sources: US Food & Drug Administration (FDA); American Academy of Dermatology.
