Poison Sumac, oak and ivy are all plants in the Toxicodendron family. They often cause an allergic reaction called contact dermatitis, which often results in an itchy, red rash that often takes the form of tiny blisters. Contact dermatitis is the most commonly diagnosed skin problem in people who have been in contact with plants.


The rash caused by one of these plants is caused by skin contact with the oils in them. They are called urushiol (pronounced Yoo-ROO-shee-all), which is commonly found all types of in poison sumac, oak, and ivy plants. There are a few ways to get a rash from them including:

  • Touching or rubbing up against any part of the plants, including the stems, flowers, leaves, stocks, berries or roots.
  • Touching any items that have come into contact with the plants such as camping and sporting gear, clothing, gardening tools, and pets.

A rash caused by poison sumac, oak or ivy cannot be spread from person to person even if you touch the liquid inside of the blister. When you or someone else breaks out in a rash, it is from coming into contact with the oil. You immune system sees it as a threat and act immediately. Some people have more severe reactions than others.


If you think you have come into contact with one of these plants and have a rash you should look for the following symptoms:

  • Small bumps or hives
  • Blisters which leak fluid, they can be of varying sizes
  • Red areas or streaking across your skin where you can into contact with the plant.
  • Itching

In some cases a reaction to one of these plants is quite severe. For those who have a severe reaction, even a small amount of the oil can cause serious symptoms such as the following:

  • Swelling in the face, mouth, tongue, genitals and neck
  • Large blisters that become widespread and leak a large amount of fluid.
  • Eyelids that have swollen shut

If you’ve never had a reaction to poison sumac, oak or ivy a rash may take one to two weeks to manifest itself. Once you have had an initial reaction to the plant, future contact usually causes a rash in one to two days. You may find that the rash has popped up on several parts of your body over the course of the first week or so, but you won’t get a rash in any place that the oil didn’t touch your skin.

For most people a rash from one of these plants only lasts one to three weeks, but could last up to six weeks in more extreme cases.


A dermatologist or doctor can usually diagnose a rash from poison sumac, oak or ivy simply by looking at it and obtaining answers to the following questions:

  • Have you been exposed to any of these plants, if so, when?
  • How long did it take for the rash to develop?
  • Have you had any rashes that were similar in the past
  • How do you spend time outdoors?
  • What are your work and hobbies as they relate to the outdoors?


Most people do not go to the dermatologist for treatment of a rash caused by these plants. They are usually simple to take care of. In the event that you develop a rash you can do the following at home to treat it.

  • Soak the area in cool area or apply a cool wet washcloth
  • Calamine lotion will help to relieve itching
  • Do not scratch, this will only make the rash worse and puts you at risk for skin infections.

The itching associated with these rashes can be quite severe but there are certain medications you should avoid as they can cause allergic reactions by themselves.

  • Topical anesthetics such as benzocaine (Lanacane)
  • Topical antibiotics such as neomycin (Neosporin)

If the rash covers a large portion of your body or you have other severe symptoms you should consult your doctor immediately. They may prescribe a corticosteroid cream to help get rid of the rash. If the rash is severe or refuses to go away, you may be given corticosteroid pills or injections.

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