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The St. Louis Dermatology Guide to Treating Poison Ivy Rash

Small coalescing blisters of poison ivy
Poison Ivy Rash - St. Louis

With spring finally, here, St. Louisans are increasingly outside walking, hiking, and gardening and consequently at increased risk for exposure to plants and flowers. If you've ever come into contact with poison ivy, oak, or sumac, you know how uncomfortable and itchy the resulting rash can be. Even though it's not contagious, the rash can be quite persistent and long-lasting. Here is a guide from our dermatologists discussing everything you need to know about poison ivy rash and how to treat it.

What Causes Poison Ivy Rash?

Poison ivy, oak, and sumac contain a sticky oil called urushiol, which is what causes the rash. When you come into contact with the oil, it can penetrate your skin within minutes, causing an allergic reaction in some people. The rash usually appears in the area that came into contact with the oil.

Symptoms of Poison Ivy Rash

Poison ivy rash usually appears in a straight line or streak, reflecting how the plant brushed against your skin. It typically begins with itching and redness, followed by bumps and blisters that can ooze fluid. The rash can also cause swelling and inflammation.

What to Do If You Come into Contact with Poison Ivy?

If you think you've come into contact with poison ivy, act quickly to prevent the rash from developing or worsening. Here's what to do:

  1. Wash your skin immediately with lukewarm water and soap, including under your nails.

  2. Wash your clothes and any objects that may have come into contact with the oil, such as gardening tools.

  3. Apply cool compresses to the affected area to help soothe the itching and inflammation.

If you develop a rash despite your best efforts, there are a few things you can do to ease your symptoms.

Treating Poison Ivy Rash

  1. Calamine lotion: This over-the-counter lotion can help soothe the itchiness and dry out the blisters.

  2. Oatmeal bath: Adding colloidal oatmeal to your bathwater can also help soothe the itching and inflammation.

  3. Hydrocortisone cream: This cream can help reduce redness, itching, and swelling.

  4. Antihistamines: Taking an over-the-counter antihistamine can help relieve itching and swelling.

If the rash is severe, contact us at 314-994-0200 to be evaluated by one of our dermatologists. They may prescribe a steroid cream or pills or injection, to help quickly reduce inflammation and itching.


The best way to prevent poison ivy rash is to avoid coming into contact with the oil in the first place. Here are a few tips:

  1. Learn to recognize poison ivy, oak, and sumac plants, and avoid touching them.

  2. Wear protective clothing, such as long sleeves and pants, when you're in areas where these plants are present.

  3. Use a barrier cream containing bentoquatam before going into areas where poison ivy may be present.

  4. Wash your skin and clothing immediately after coming into contact with these plants.


Poison ivy rash can be uncomfortable and persistent, but with prompt treatment, you can ease your symptoms and speed up the healing process. If you're unsure whether you've come into contact with poison ivy, it's always best to err on the side of caution and take steps to prevent the rash from developing. If you develop a rash, don't hesitate to seek medical attention if your symptoms are severe or if the rash is on your face or genitals. At Mid-County Dermatology located at Missouri Baptist Medical Center, our board-certified dermatologists can provide prescription treatment to help alleviate your symptoms and promote healing.

Here is more information about poison ivy.

Be on the lookout for more skin tips and advice from our St. Louis Dermatology team!

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