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Poisonous Plants: Ivy, Oak, and Sumac: Beware the Oils

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 Poison

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:

  1. Touching the sap —Contact with the sap of a poison ivy, oak, or sumac plant exposes you to urushiol. And since urushiol remains active for months, this includes coming into contact with dormant or dead plants.
  2. Carriers of the poison —Anything that comes into contact with the oily urushiol will be a conduit, including skin, clothing, backpacks, tools, and carpeting. It is even possible to become infected by handling firewood that has lingering traces of poison ivy, oak, or sumac.
  3. Furry friends —Pets are an especially good conduit for urushiol. While their fur protects them from getting the rash, the urushiol readily sticks to their fur, and then spreads to anything that touches it, including you.
  4. Through the air —When poison ivy, oak, or sumac is burned, airborne urushiol particles can come in contact with the skin and cause a rash. If inhaled, these particles can cause a rash in the lungs, a serious condition. Accordingly, you should never try to remove or dispose of these poisonous plants by burning them.

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:

  1. Cover up skin —When walking or working in areas where these poisonous plants may lurk, wear long-sleeved shirts and pants and tuck your pant bottoms into your socks. Next, become familiar with what these plants look like, and avoid them. Since they can grow in somewhat different configurations, the old adage of "Leaves of 3, beware of me" tends to be of only limited help. You can find pictures of poison ivy, oak, and sumac on the American Academy of Dermatology website.
  2. Clean up —If any of your clothing, tools, furniture, or carpeting comes in contact with urushiol, wash them thoroughly, being careful not to transfer the urushiol to your skin. Do the same with a pet that has been exposed to urushiol.
  3. Hire help —It is best to hire a professional to remove poisonous plants from around your house or garden. However, if you decide to do it yourself, be sure to pull the entire plant (including the roots) and wear clothing protecting as much of your skin as possible. Never burn the plants.
  4. Skin care —You can apply a skin care product called IvyBlock that prevents skin from absorbing urushiol.

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: Updated July 15, 2016. Accessed May 9, 2017.

Poison ivy. Family Doctor—American Academy of Family Physicians website. Available at: Updated April 2014. Accessed May 9, 2017.

Poison ivy, oak, and sumac. American Academy of Dermatology website. Available at: Accessed May 9, 2017.

Last reviewed May 2017 by Michael Woods, MD, FAAP  Last Updated: 5/9/2017