Poison Ivy: 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 Monday morning the three were scratching furiously. By mid-afternoon, they were in the doctor's office. The diagnosis? Poison ivy.
Poison ivy, as well as poison oak and poison sumac, grows almost anywhere—deep in the woods, at the local park, or 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.
The full-blown rash usually develops within 12-72 hours, but people who have never been exposed to poison ivy may not see a full-blown rash for 7-10 days. Although the itching and swelling can be treated and controlled, there is no cure per se 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. 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. So if you know you have come in contact with it, the best treatment is to wash the contaminated skin in cold water 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 very loosely since contact with the air helps heal the rash. 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 (eg, garden tools, sports equipment, etc.). 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 physician or dermatologist will generally prescribe prescription-strength cortisone creams, or in extremely severe cases, oral steroids, 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.
American Academy of Dermatology
American Academy of Family Physicians
Canadian Dermatology Association
Canadian Family Physician
Outsmarting poison ivy and its cousins. United States Food and Drug Administration website. Available at: http://www.fda.gov/fdac/features/796_ivy.html.
Poison plants: ivy-sumac-oak. American Academy of Dermatology website. Available at: http://www.aad.org/pamphlets/PoisonIvy.html. Accessed September 19, 2011.
Last reviewed September 2011 by Brian Randall, MD