Poisonous Plants

Originally published on 08/02/2019

Poisonous plants are common on or near construction sites. Most people develop a skin rash and skin irritations lasting up to three weeks when they contact poison ivy or poison oak. The reaction is caused by urushiol (“oo-roo-shee-ohl”) oil found in the sap. The oil is in the stems, leaves and berries of these plants and can be transmitted by brushing against the plant, or from secondary contact with animals or clothing.

Poison ivy

Found throughout the United States, except in the Southwest, Alaska and Hawaii, poison ivy has three shiny green leaves, a red stem and typically grows in the form of a vine, often along riverbanks, roadsides and woodlands. Old vines are very hairy; in late summer and fall the vines will have green-to-white berries. Poison ivy is most dangerous in the spring and summer, when they have plenty of sap and a high content of urushiol. However, cases have been reported in people who used the twigs of the plant for firewood or the vines for Christmas wreaths. Even dead plants can cause a reaction, because the oil remains active for several years after the plant dies.

Poison oak

Poison oak grows as a low shrub in the eastern part of the U.S. (from New Jersey to Texas), and as 6-foot-tall clumps or vines up to 30 feet long along the Pacific coast. It has oak-like leaves, usually in clusters of three and clusters of yellow berries.

Treatment if you’re exposed:

  • First, cleanse the exposed skin with generous amounts of isopropyl (rubbing) alcohol. (Note: alcohol removes your skin’s natural protection along with the urushiol, so avoid any additional contact because skin washed with alcohol will allow the urushiol to penetrate twice as fast.)
  • Second, wash the affected area with water.
  • Third, take a regular shower with soap and warm water. Do not use soap before this point because soap tends to pick up some of the urushiol from the skin’s surface and move it around.
  • Clean clothes, shoes, tools and anything else that may have been in contact with the urushiol with alcohol and water, then wash with soap and water. Be sure to protect your hands during this process.
  • To help reduce the itchiness, apply lotions with an anti-inflammatory and cooling effects (talc, calamine). Oral antihistamines can also relieve itching.

Poison ivy blisters don’t contain urushiol, so any oozing fluid is not contagious and will not spread the rash further. A rash will only occur where urushiol has touched the skin. However, the rash may seem to spread if it appears over time instead of all at once, because the urushiol is absorbed at different rates in different parts of the body, is trapped under the fingernails, or because of repeated exposure to contaminated objects.

The American Academy of Dermatology recommends that people who have had severe reactions in the past to any of these plants, contact a dermatologist as soon as possible after a new exposure.

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