Poison Ivy, Oak, and Sumac Information Center


Frequently Asked Questions (FAQ)

Note: This page is not an advertisement for any particular product and all opinions contained here are solely those of the individual contributor.

What are the symptoms of Poisoning?
The first symptom of poisoning is a severe itching of the skin. Later, a red inflammation and a blistering of the skin occurs. In severe cases, oozing sores develop. The rash spreads by the poisonous sap (urushiol), not as the result of contamination from sores. The blood vessels develop gaps that leak fluid through the skin, causing blisters and oozing. When you cool the skin, the vessels constrict and don't leak as much according to Robert Rietschel, M.D. Chairman of Dermatolgy at New Orleans' Ochsner Clinic.

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Note: The zanfel site now has an excellent series of rash pictures.


How does Poisoning Occur?
Poison ivy, western poison oak, and poison sumac have the poisonous sap (urushiol) in their roots, stems, leaves and fruit. The sap is released when the plant is bruised, making it easier to contract Rhus-dermatitis in the spring and early summer when leaves are tender. The sap may be deposited on the skin by direct contact with the plant or by contact with contaminated objects, such as shoes, clothing, tools and animals. Severe cases have occurred from sap-coated soot in the smoke of burning plants. Because urushiol is inside the plant, brushing against an intact plant will not cause a reaction. But undamaged plants are rare because "Poison oak, ivy and sumac are very fragile plants," says William L. Epstein, M.D., professor of dermatology, University of California, San Francisco. Stems or leaves broken by the wind or animals, and even the tiny holes made by chewing insects, can release urushiol.

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Can I spread it by Scratching?
"Rhus plants(poison ivy, poison oak, poison sumac) are the most common cause of allergic contact dermatitis in the US. Rhus plans contain the potent antigen urushiol, which will sensitize 60% to 80% of the persons who are exposed to it. ...(It) may be carried on the fur of pets, clothing, shoes, toys, tools, or other objects and then transferred to the skin. Approximately 24 to 36 hrs after a sensitized person is exposed to the urushiol, a blistery, itching rash develops. Usually within 15 minutes of contact, the urushiol binds to skin proteins. If it is washed off with soap and water before that time, a reaction may be prevented. After the antigen is fixed, however, it cannot be washed off or transferred to other areas. Scratching or oozing blister fluid cannot spread the antigen to other areas of the body or to other persons. New lesions that appear a few days after the primary lesions represent less sensitive areas or areas where less antigen was deposited, not spreading of the antigen. Because the course of the reaction usually is 12 to 15 days, 2 weeks of medication should be prescribed. Reference [Dermatology in Primary Care 1994]

Once bound to cell membranes, urushiol is virtually impossible to wash off and attached to cell membranes becomes a "warning flag" that attracts patrolling T-cells and initiates a full-blown immune response. Reference [Herbalgram (American Botanical Council) Volume 34: 36-42, 1995 by W.P. Armstrong and W.L. Epstein, M.D.]

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Charles H. Booras, M.D. Karl Hempel, M.D. Dr Greene's, House Calls
Dr William E. Jones, M.D. Lisa A. Garner, MD


How do I deal with the Rash?
After the oil has touched the skin, it usually takes some time for it to penetrate and do its damage. Before this happens, it is wise to wash the skin thoroughly several times with plenty of soap and water. Care should be taken not to touch any part of the body, for even tiny amounts of the oil will cause irritation. If poisoning develops, the blisters and red, itching skin may be treated with dressings of calamine lotion, Epsom salts, or bicarbonate of soda. Scientists have developed a vaccine that can be injected or swallowed. But this is effective only if taken before exposure.

If you don't cleanse quickly enough, or your skin is so sensitive that cleansing didn't help, redness and swelling will appear in about 12 to 48 hours. Blisters and itching will follow. For those rare people who react after their very first exposure, the rash appears after seven to 10 days.

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How do I identify the plants?
The compound leaves of poison ivy consist of three pointed leaflets; the middle leaflet has a much longer stalk than the two side ones. The leaflet edges can be smooth or toothed but are rarely lobed. The leaves vary greatly in size, from 8 to 55 mm (0.31" to 2.16") in length. They are reddish when they emerge in the spring, turn green during the summer, and become various shades of yellow, orange or red in the autumn. Small greenish flowers grow in bunches attached to the main stem close to where each leaf joins it. Later in the season, clusters of poisonous, berrylike drupes form. They are whitish, with a waxy look.

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Contrary to many written reports, poison ivy leaves are not strictly shaped. You'll find in the same patch leaves that are elongated and lobed, smoothed and toothed, small and large. Identification of the plant including its variations can be difficult. The first picture collection below shows a sampling of poison ivy plants with various leaf shapes.

Picture Collections: poison ivy (NEW) / poison oak / poison ivy / poison sumac / similar looking plants

Here is a nice site with lots of pictures and a quiz. Another site with a poison ivy pictures quiz.

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Do other plants have urushiol?
Yes, as a matter of fact, a number of the members of the Sumac family contain urushiol. These include the cashew nut shell, mango, Rengas tree, Burmese lacquer tree, India marking nut tree, and Ginkgo biloba. These are all members of the Anacardiaceae family (or commonly named "cashew") which comprises about 70 genera and 850 species of trees and shrubs. Below are links sites with extensive information about other plants of the Anacardiaceae family and which have urushiol.


Where are these plants found?
Poison ivy is a harmful vine or shrub in the cashew family. It grows plentifully in parts of the United States and southern Canada. Poison ivy usually grows as a vine twining on tree trunks or straggling over the ground. But the plant often forms upright bushes if it has no support to climb upon. Species related to poison ivy include poison oak, which grows in the Pacific Northwest and nearby regions of Canada, and poison sumac, which grows in the Eastern United States. Poison oak and poison sumac both are shrubs. The tissues of all these plants contain a poisonous oil somewhat like carbolic acid. This oil is extremely irritating to the skin. It may be brushed onto the clothing or skins of people coming in contact with the plants. Many people have been poisoned merely by taking off their shoes after walking through poison ivy. People can get poisoned from other people, but only if the oil remains on their skin. The eruptions themselves are not a source of infection.

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How do I control Poison Ivy, Oak or Sumac plants?
Efforts have been made to destroy these plants by uprooting them or by spraying them with chemicals. But poison ivy and poison oak are so common that such methods have not been very effective in eliminating them. Contact with the plants should be avoided.

Removal and Control


What is the Scientic Classification?
Poison ivy, poison oak, and poison sumac belong to the cashew family, Anacardiaceae. Poison ivy is classified as Rhus radicans or Toxicondendron radicans. Poison oak is Rhus diversiloba or Toxicondendron diversilobum and poison sumac is Rhus vernix or Toxicondendron vernix.

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