Poison Ivy, Oak, and Sumac: Symptoms and Signs

What are the signs and symptoms of the poison ivy, poison oak, and poison sumac rash?

Signs and symptoms are related both to the sensitivity of the individual as well as the severity of exposure. While over half of people are sensitive to poison ivy, oak, or sumac and will react by developing the characteristic rash, about a significant percentage of the population is highly sensitive and may have particularly severe symptoms or develop symptoms after a very mild exposure.

The rash usually starts one or two days after exposure, though the delay between contact and its onset can be longer, up to several days. This may lead to confusion over where the exposure took place. The first signs of the rash are curved lines of red, itchy bumps or blisters. These continue to appear for many days, even up to two to three weeks due to a slow reaction to absorbed urushiols and depending on how much resin touched the skin at a given point. This makes it seem as though the rash is "spreading," although the fluid in blisters is just part of the allergic reaction and contains no chemicals or bacteria. It also makes it appear that there may still be poison ivy in clothes and/or on pets. Although this is theoretically possible, repeated washing of these often produces no improvement.

In rare situations, the eyes, airway, and lungs may be affected if exposed to smoke from burning plants.

Poison ivy, oak, or sumac is not contagious, neither from one person to someone else nor from one part of the body to another.

Many references emphasize that animals can carry the poisonous resin. There's no doubt this is true, but its practical significance may be limited. The first sign of poison ivy, after all, is usually a curved line of rash on the skin. Your poison ivy is more likely to have come from a stem or leaf that dragged against the skin, not from your pet.

Is a rash from poison ivy, oak, and sumac dermatitis contagious?

The rash from poison ivy, oak, or sumac is not contagious. It cannot be spread to other parts of the body or to other people. However, if you still have traces of the plant oil (urushiol) on your hands after exposure, you can spread it to other people and to other parts of your body. Sometimes, the rash will take longer to appear in some areas of the body than in others, giving the appearance that the reaction has spread elsewhere in the body. However, only contact with the sap oil urushiol can spread the reaction, and the rash itself does not contain urushiol.

How is the dermatitis of poison ivy, oak, or sumac diagnosed?

The diagnosis is generally established upon observation of the typical rash in an area that could have been exposed to the plants, along with a history of potential exposure (such as weeding a garden or walking in the woods). No special tests are required for the diagnosis. In some cases, skin inflammation due to other causes (including allergic contact dermatitis or chemical irritation) may be mistaken for poison ivy, oak, or sumac since the rash may be similar.


Allergies can best be described as: See Answer

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Medically reviewed by Avrom Simon, MD; Board Certified Preventative Medicine with Subspecialty in Occupational Medicine


Stephanides, Steven L., and Chris Moore. "Plant Poisoning, Toxicodendron." eMedicine.com. Aug. 18, 2009. <http://emedicine.medscape.com/article/817671-overview>.