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Poison Ivy

What Is Poison Ivy?

Leaves of three — let them be! You've probably heard that little rhyme about poison ivy, the plant that can cause an itchy rash. But did you know that poison ivy, poison oak, and poison sumac all contain the same rash-causing substance?

It's called urushiol (say: yoo-ROO-shee-ol), a colorless, odorless oil (or resin) found in the leaves of the plants.

What Are the Signs & Symptoms of Poison Ivy?

Urushiol is considered an allergen because it causes an allergic reaction — the rash and sometimes swelling. Not everyone will get a reaction, but most people will.

This reaction can appear within hours of touching the plant or as late as 5 days later. Typically, the skin becomes red and swollen and blisters will appear. It's itchy, too. After a few days, the blisters may become crusty and start to flake off. It may take 2 to 3 weeks to heal.

this red, bumpy, itchy rash is a typical allergic reaction to poison ivy

When Should I See the Doctor?

It's a good idea to see your doctor if you have any kind of rash, especially if you have a fever too. If your rash was caused by poison ivy or a similar plant, the doctor may recommend cool showers and calamine lotion.

In more severe cases, a liquid or pill medicine called an antihistamine might be needed to decrease itching and redness. A steroid (say: STER-oyd), another kind of medicine, may be prescribed in some cases. This medicine may be applied directly to the rash or taken in a pill or liquid form.

Is Poison Ivy Contagious?

The poison ivy rash itself isn't contagious. But it's possible to get a poison ivy rash without ever stepping into the woods or directly touching one of the plants. Here's how: Urushiol can pass from one person to another. Plus, a person can pick it up from anything that's come in contact with the oil, including your dog that likes to roam the woods! Urushiol even can travel through the air if someone burns some of the plants to clear brush.

How Can I Prevent Rashes From Poison Ivy?

To avoid getting a poison ivy rash:

  • Learn to identify poison ivy, oak, and sumac, so you can steer clear of them. The leaves of poison plants release urushiol when they're "injured," meaning if they get bumped, torn, or brushed up against. Once the urushiol has been released, it can easily get on a person's skin. When the oil is released, the leaves may appear shiny or you may see black spots of resin on them.
  • Avoid areas where you know these plants live.
  • Wear long sleeves and long pants when you're in areas that could contain poison plants.

If you come into contact with urushiol oil, try to wash it off your skin right away. But don't take a bath! If you do, the oil can get in the bath water and spread to other areas of your body. Take a shower instead, and be sure to use soap. And if your dog has been out exploring the woods, you might want to give your pet a shower too!

Date reviewed: August 2019