Poisonous Plants: Ivy, Oak, and Sumac: Beware the Oils
by Rick Alan
As the temperature rises, so do your opportunities to commune with nature. Do not let poison ivy ruin your plans.
One beautiful summer day, Joanna recruited her two young children to help her work in the backyard. After working in the vegetable garden, she and her kids turned their attention to the patch of weeds growing at the back of the yard and along one side of the house.
The next morning, Johanna awoke to find a slightly uncomfortable rash erupting on her arms and lower legs. So did her daughters. Over the course of the day, their rashes grew progressively worse. By the second morning, the three were scratching furiously. By mid-afternoon, they were in the doctor's office. The diagnosis? Poison ivy.
Poison ivy, oak, and sumac grow almost anywhere—deep in the woods, at the local park, in the sand dunes at the beach, and in your yard.
The culprit behind the extremely uncomfortable allergic skin rash of poison ivy, oak, and sumac is urushiol (pronounced "you-ROO-shee-ol"), an oily substance found in every part of the plant except the pollen. Upon contact with the skin, urushiol is almost immediately absorbed. If not removed quickly—within about 10 minutes—an allergic reaction (in most people) begins with redness and swelling followed by extreme itchiness, and then by blisters (filled with a yellowish fluid) that can break open, causing crusting and scaling.
Most people develop a rash within 12-72 hours of exposure. But, depending on the amount of exposure, it may be longer. Although the itching and swelling can be treated and controlled, there is no cure for the rash itself, which usually takes 1-3 weeks to run its course.
Catching the Rash
Most people do not develop a rash upon first exposure, but rather after repeated exposures, and some will never react. In addition, sensitivity to urushiol often decreases with age, so children tend to be much more susceptible to urushiol-caused rashes than adults.
Despite what you may have heard, you cannot catch the rash from someone who has it, nor can you spread the rash from one part of your body to another by scratching. You must have direct contact with urushiol yourself.
However, you can come into contact with urushiol in a number of ways:
Treatment at Home
It takes about 10 minutes for urushiol to be fully absorbed into the skin. If you know you have come in contact with it, the best treatment is to wash the contaminated skin with cool water, with or without soap, as soon as possible. Once the rash has developed, there are a number of treatments that will lessen its severity, including:
If you cover the rash or blisters after applying cream or lotion, do so with a gauze pad, and cover them loosely so you do not rupture the blisters. Avoid scratching the rash and do not break open the blisters caused by the rash. Though the liquid within the blisters will not spread the rash, bacteria on the fingers and under the fingernails can cause the rash and/or blisters to become infected.
Wash anything you wore, including your shoes, during the time you came in contact with poison ivy, oak, or sumac. Use hot, sudsy water. Also wash anything else that might have come in contact, such as garden tools or sports equipment. You can use rubbing alcohol or a mix of water and bleach.
When to See a Doctor
Although poison ivy, oak, and sumac usually can be treated without medical attention, see a doctor if:
In such cases, your doctor or dermatologist will generally prescribe prescription-strength cortisone creams. In extremely severe cases oral steroids may be used to control itching and swelling. In addition, since airborne urushiol particles pose an extreme health danger, seek immediate medical attention if you think you or your child has inhaled such particles, even if symptoms have not yet occurred.
The best way to avoid getting a poison ivy, oak, or sumac rash is to avoid contact with urushiol. Take these steps to protect yourself:
American Academy of Dermatology
Family Doctor—American Academy of Family Physicians
Canadian Dermatology Association
The College of Family Physicians of Canada
Contact dermatitis. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T114930/Contact-dermatitis. Updated July 15, 2016. Accessed May 9, 2017.
Poison ivy. Family Doctor—American Academy of Family Physicians website. Available at: https://familydoctor.org/condition/poison-ivy. Updated April 2014. Accessed May 9, 2017.
Poison ivy, oak, and sumac. American Academy of Dermatology website. Available at: https://www.aad.org/public/diseases/itchy-skin/poison-ivy-oak-and-sumac. Accessed May 9, 2017.
Last reviewed May 2017 by Michael Woods, MD, FAAP
Last Updated: 5/9/2017
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