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Tuesday - January 26, 2016

From: San Francisco, CA
Region: Select Region
Topic: Poisonous Plants, Shrubs, Vines
Title: Western Poison Oak Sap Transfer
Answered by: Anne Van Nest

QUESTION:

My partner is a park ranger and constantly exposed to poison oak. He gets infected sometimes but mostly seems to tolerate it pretty well. I, on the other hand, keep getting reinfected with it, all over my body, and badly. We are pretty careful not to touch until he is out of his work clothes. So I am wondering if I am getting poison oak from objects such as the plastic laundry basket he puts his dirty clothes in, or the bedspread he might sit on before changing, or his coat hanging in the entryway which might brush mine? In other words, how long do the oils linger on porous and non-porous objects? And if they do last long, any suggestions on decontaminating everything? Thank you very much for any information!

ANSWER:

Pacific poison oak (Toxicodendron diversilobum) is not a shrub to take lightly (just like its relative poison ivy (Toxicodendron radicans) to the east. You are on the right track by scrutinizing every action that might transfer the sap from clothes, boots, tools, etc. Keep up the investigation and don't let up even for one occasion.

Wikipedia says it is a woody vine or shrub inhabiting conifer, mixed broadleaf forests, woodlands, grasslands and chaparral biomes. Like poison ivy, poison oak causes itching and allergic rashes in many humans after contact by touch or smoke inhalation.

Poison oak leaves and twigs have surface oil, urushiol which causes allergic reaction in 4/5ths of humans. Before the urushiol has been absorbed by the skin, it can be removed with soap and water. However, 50% of urushiol can be absorbed within 10 minutes. Once it penetrates the skin, it can't be removed with water.

UCDavis suggests that rubbing alcohol and cold water be used to wash within 5 minutes of exposure to the urushiol.

The bad news is that urushiol, the plant oil is extremely stable and can stay active for many years in the right conditions, the www.poison-ivy.org website says that the underside of your lawn mower can still transfer the oil in the spring from last fall.  They also say that clothes should be washed by themselves with laundry detergent and bleach.  Tools and shoes should also be cleaned with rubbing alcohol while wearing rubber gloves.

Another informative website is the Poison Ivy, Oak and Sumac Information Center. They say that 1 billionth of a gram is all that is needed to cause a rash. Specimens of urushiol several centuries old have caused dermatitis in sensitive people. Also 1-5 years is normal for urushiol oil to stay active on any surface including dead plants. Rubbing the rash won't spread poison ivy to other parts of your body (or to another person). You spread the rash only if urushiol oil has been left on your hands.

 

From the Image Gallery


Eastern poison ivy
Toxicodendron radicans

Eastern poison ivy
Toxicodendron radicans

Eastern poison ivy
Toxicodendron radicans

Eastern poison ivy
Toxicodendron radicans

Eastern poison ivy
Toxicodendron radicans

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