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Poison Oak: This Cousin is Just as Irritating as Poison Ivy

Pacific poison oak. Photo by Gary A. Monroe, courtesy


Characteristics of Poison Oak

Poison oak is one of the “big three” rash-producing, woody plants, along with poison ivy and poison sumac. All belong to the same plant genus (Toxicodendron), and contain the oil urushiol. It is this substance that causes blistering skin rashes in 85% of those who come into contact with it.

Common along the Pacific coast, Western poison oak grows as a dense shrub in fields, woods, and other undisturbed areas. It also vines up trees or creeps as a groundcover. Closely related Atlantic poison oak grows in the South, lower Midwest and as far north and east as Pennsylvania and New Jersey. Both species spread primarily by seeds enclosed in their creamy-white berries. They are identified by their leaves composed of three leaflets, the middle one slightly larger. Glossy, bronzy young foliage becomes green in summer, and turns orange-red in fall.

Atlantic poison oak. Photo by Robert H. Mohlenbrock, courtey

Getting Rid of Poison Oak

Repeated cutting and digging of established poison oak plants will sap energy and eventually kill them. If possible remove plants when they are young and more shallowly rooted. Be sure to wear gloves, protective clothing, and eyewear while handling plants. Protective skin creams may help prevent a reaction. Do NOT attempt to weed-whack poison oak — you’ll spew the allergenic oil everywhere. Afterward, wash all gloves and garments in very hot water separately from a general laundry load to remove the rash-causing oil from the fabric. Clean contaminated tools thoroughly. Take the same precautions when removing dead, or leafless poison oak plants in winter. All parts of the plant contain urushiol, and the oil continues to cause rashes for years after a plant has died. Also, don’t burn poison oak — urushiol-laced smoke can cause serious irritation to lung linings.

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