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Poison Ivy, Oak and Sumac
Question: Which of these two plants are poisonous? Poison Ivy

 

 

Poison Oak Answer: They both are. The plant on the left is poison ivy, and the plant on the right is poison oak. (photo of poison oak courtesy of Jeff McMillian)  

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"Leaves of three, leave them be"
Knowing what to avoid when working in the yard and walking through the woods is always a good idea, but this is not a foolproof way to avoid a troublesome rash. Poison ivy and its relatives are often mixed in with other vegetation and frequently not even noticed until it's too late. Wearing gloves when working in the yard, and keeping the skin covered in situations when exposure is hard to avoid, is the best way to prevent the rash.


Plant Identification

Poison Ivy:

Poison ivy plants have leaf arrangements that are clustered in groups of three leaflets, but it may vary from groups of three to nine. Two leaflets grow on opposing sides and the third stands by itself at the end of the stalk, as in the photo to the right. In each cluster, the middle leaf grows on a stalk that is much longer than those on the sides.

Generally found east of the Rocky Mountains, poison ivy (Toxicodendron radicans) is an adaptable, woody perennial weed.

It can grow as a shrub or form a vine. Some poison ivy plants may carpet the ground while others climb tree trunks, stone walls, and fences. When it grows among other vines, it is more difficult to recognize.

It can grow in the open sun or in deep shade.

The edges of the leaflets may be smooth, lobed or toothed.

Poison ivy leaflets sometimes have hairy undersides. Its stems are woody. The aerial rootlets make the stem look like a fuzzy rope.

Poison Ivy
New springtime growth is often reddish and especially shiny. After the leaves emerge, the plants may develop a cluster of greenish flowers. Poison ivy fruit has a white, waxy appearance, a smooth surface and looks like mistletoe. Summertime foliage is either dull or glossy green. Fall foliage can be yellow, red or orange. (Photos and text from Univ of Connecticut, Integrated Pest Management) Poison Ivy
The appearance of poison ivy can vary considerably from region to region, and season to season. This is a photo of Poison Ivy in Atlanta, Georgia courtesy of Center for Disease Control Poison Ivy
Virginia Creeper

Virginia Creeper: This plant is often confused with Poison Ivy. A clear distinction between the species is that eastern poison ivy has three leaflets and Virginia creeper has five leaflets. Some literature suggests that Virginia Creeper is not poisonous, but the sap of the plant contains oxalate crystals and can cause skin irritation and rashes in some people.

Virginia Creeper grows as a vine, reaching heights of 30 feet or more. The plant forms a network of stems that cement themselves to structures and will grow up any tree and most shrubs. This species will slowly kill the host on which it is growing, because it often prevents the host from receiving an adequate amount of sunlight and can crowd out or choke other plants.

The leaves of new growth are reddish then they become green. In the fall they turn a bright red. Virginia Creeper frequently grows alongside of poison ivy. (6,7)

What is so poisonous about poison ivy?

Although poison ivy is probably responsible for more itchy rashes than any other plant, the plant oil, urushiol, is the real culprit and is in poison ivy, poison oak, and poison sumac as well. In general, about 85% of people are sensitive to the plant oil, uroshiol. It is present in all parts of the plants, including the leaves, stems, flowers, berries, and roots.

Soon after the skin comes in contact with the oil, it is quickly absorbed into the skin and may remain active on clothing, tools, and even pet fur for long periods of time. Petting an animal that has been in contact with the plant can potentially cause a rash. Small amounts of the oil can even remain under a person's fingernails for a period of time unless it is deliberately removed by meticulous cleaning.

Contact with these plants is most dangerous in the spring and summer, when there is plenty of sap, the urushiol content is high, and the plants are easily bruised. However, the danger doesn't disappear over the winter. Dormant plants can still cause reactions, and cases have been reported in people who used the twigs of the plant for firewood or the vines for Christmas wreaths. Even dead plants can cause a reaction, because urushiol remains active for several years after the plant dies. (1)

Smoke from burning plants also contains the oil and may cause a severe, even life-threatening, reaction in certain people. Smoke from this oil can affect the eyes, airway, and lungs. Nearly one-third of forestry workers and firefighters who battle forest fires in California, Oregon and Washington develop rashes or lung irritations from contact with poison oak, which is the most common of the three in those states.(1)

Eating a small amount of the urushiol can result in a life-threatening reaction involving the gastrointestinal tract.(4)

Other plants that contain uroshiol and can cause a rash:

Poison Oak:

  • Leaves are clustered in groups of 3 leaflets
  • Leaves are smooth-edged and lobed like those of an oak leaf
  • Usually grows as a small bush but sometimes as a climbing vine
  • Found most commonly West of the Rockies

Poison Oak by J McMillian
Photo courtesy of Jeff McMillian, almostedenplants.com/USDA.gov

Poison Oak
Photo of poison oak courtesy of
D. Moorhead/Bugwood.org

 

Poison Sumac: Less common than poison ivy and poison oak and found only in extremely wet areas of Eastern United States

  • There are groups of 7-13 leaflets on each stem. It is always an odd number because while most of the leaflets form matching pairs (one across from the other), there's always one lone leaflet at the tip of the compound leaf, which gives it the shape of a feather.
  • Leaves are smooth and oval-shaped
  • The stem of the leaves are red
  • Berries are glossy pale yellow or cream-colored
  • Rangy shrub up to 15 feet tall

Poison Sumac Poison Sumac
Photo by William S. Justice @ USDA-NRCS PLANTS Database, courtesy of Smithsonian Institution

Symptoms of Poison Ivy, Oak, or Sumac

Poison ivy rashIndividual sensitivity to poison ivy varies greatly. Natural immunity is originally present in all persons, but is reduced through time by contact with the poison.(6)

When urushiol gets on the skin, it begins to penetrate in minutes. A reaction appears, usually within 12 to 48 hours. Symptoms include intense itching, a red rash, followed by multiple fluid-filled blisters, which may be tiny or very large. In a few days, the blisters become crusted and take 10 days or longer to heal. Photo of rash from poison ivy, courtesy of the Center for Disease Control

The blisters typically occur in a straight line following the track where the plant brushed along the skin. The rash may appear at different times in different locations either because of repeat contact with contaminated clothing and other objects or because some parts of the skin are more sensitive than others, or because urushiol absorbs more slowly into skin that is thicker such as on the forearms, legs, and trunk. Although a common misconception, fluid from the vesicles of a poison ivy rash does not contain urushiol, is not an allergen source for new lesions, and is not contagious.

The severity of the rash can be variable and range from a localized mild red rash with itching to a diffusely reddened, swollen, severely painful and intensely pruritic rash with bullous lesions. Secondary infection can complicate the rash.

Poison plant dermatitis can affect almost any part of the body. The rash does not spread by touching it, although it may seem to when it breaks out in new areas.

The itching and rash last for 2 to 3 weeks and new lesions may continue to appear for up to 2-3 weeks. Initially, the rash tends to occur from the slow reaction to urushiol in the sap; however, lesions that appear later are often secondary to contact with contaminated surfaces (eg, clothing, pet hair, gardening tools, camping equipment). (2, 3)

Poison Oak Rash A typical blistering poison oak rash. Note the typical linear pattern to the lesions.

The rash from poison ivy, oak, and sumac would be the same as it is due to the same allergen, the plant oil urushiol.

Photo and description courtesy of the CDC (Center for Disease Control).


Treatment

Treatment is the same for all three poisonous plants. Symptoms can be relieved with treatment, but the duration of the rash is not shortened. The rash, blisters and itch normally disappear in 14 to 20 days without any treatment, but few can handle the intense itching without some relief.

  • Once you're touched the poisonous plant, eliminate the uroshiol:

    • First, cleanse exposed skin with generous amounts of isopropyl (rubbing) alcohol. This should be done within 10 minutes of exposure. (Don't return to the woods or yard the same day. Alcohol removes your skin's protection along with the urushiol and any new contact will cause the urushiol to penetrate twice as fast.)
    • Second, wash skin with water only--no soap. (Water temperature does not matter; if you're outside, it's likely only cold water will be available.)
    • Third, take a regular shower with soap and warm water. Do not use soap before this point because soap will tend to pick up some of the urushiol from the surface of the skin and move it around
    • Clothes, shoes, tools, and anything else that may have been in contact with the urushiol should be wiped off with alcohol and water. Wash clothing in hot, soapy water. Be sure to wear gloves or otherwise cover your hands while doing this and then discard the hand covering. "Urushiol that's rubbed off the plants onto other things can remain potent for years, depending on the environment," says William L. Epstein, M.D., professor of dermatology, University of California(1).

  • Treat the rash with one of the following: (medications are listed from mildest to strongest)

    • Aveeno anti-itch cream (over-the-counter) --steroid-free cream with calamine and natural colloidal oatmeal provides temporary relief of the itching and pain associated with many minor skin irritations such as poison ivy/oak/sumac, insect bites, and chicken pox rash.

    • 1% hydrocortisone (over-the-counter) Cortaid, Lanacort, or Aveeno 1% hydrocortisone are all products with 1% hydrocortisone, a weak, nonfluorinated topical steroid. Aveeno 1% hydrocortisone anti-itch cream is a combination product which includes hydrocortisone cream with colloidal oatmeal, Aloe and Vitamin E, and provides temporary relief of the itching.
      • These products can be purchased over-the-counter, without a prescription and are considered safe and effective by the FDA for temporary relief of itching associated with poison ivy. It's important to note that only mild topical corticosteroids, such as these, should be used on the face or genitals. Stronger preparations can cause adverse side effects, such as thinning of the skin, and could thus be harmful if used on the face or genitals. Caution should be used with any occlusive dressings. Once the steroid cream is applied, covering the area with an occlusive dressing, such as a bandaid, will increase the strength and potential side effects of the steroid cream.

    • Prescription Steroids (corticosteroids): Either topical or oral are the most effective.
      • Topical: stronger than 1% hydrocortisone Small areas of severe cases of rash are treated with strong topical, prescription-strength corticosteroids, such as triamcinolone (Aristocort). Do not use any of these strong topical corticosteroids on the face or genitals.
      • Oral: If the rash is on the face, genitals, or covers more than 30% of the body oral corticosteroids are often necessary and must be taken for 14-21 days. Caution: Shorter courses of treatment will cause a rebound with an even more severe rash.(1)

  • Soaking in cool water or applying cool compresses may be helpful.

  • Oral antihistamines can help relieve itching. Diphenhydramine (Benadryl) can be purchased over-the-counter in various oral forms. It's important to read the label carefully for contraindications and side effects. Benadryl can cause extreme drowsiness; for this reason, Benadryl is often the active ingredient in over-the-counter sleep preparations. Oral Benadryl is very useful in cases when a person can't sleep because of the itching of a rash from poison ivy. Continued use of Benadryl, however, will lessen the side-effect of drowsiness.

  • Caution: Lotions and creams containing antihistamines (i.e. Benadryl Cream) are not recommended by most dermatologists.

  • Also, there are a number of over-the-counter products to help dry up the oozing blisters, including:

    • oatmeal bath products, such as Aveeno oatmeal bath, are available over-the-counter
    • aluminum acetate (Burrows solution)
    • baking soda
    • aluminum hydroxide gel
    • calamine
    • kaolin
    • zinc acetate
    • zinc carbonate
    • zinc oxide
 

Prevention

  • Bentoquatum: There is an over-the-counter skin-barrier product that contains bentoquatum. Apply this before going outdoors. It helps prevent urushiol from penetrating the skin.
  • If you find one of these plants in your yard, remove it with care. Apply a skin-barrier product and wear long pants and sleeves, heavy work gloves covered by a second pair of rubber gloves, and closed shoes or boots. Pull or dig out the entire plant, making sure to get as much of the root as possible. Avoid touching any part of the plant, and keep children and pets out of the area until you are finished. Never burn the plants. Instead, place them in a heavy, tightly sealed plastic lawn bag and dispose of them.(5) The FDA recommends checking with your municipality regarding recommended method of disposal. (1)
  • If you've been exposed to poison ivy, oak or sumac, if possible, stay outdoors until you complete the first two steps (1).
    1. First, cleanse exposed skin with generous amounts of isopropyl (rubbing) alcohol. This should be done within 10 minutes of exposure. (Don't return to the woods or yard the same day. Alcohol removes your skin's protection along with the urushiol and any new contact will cause the urushiol to penetrate twice as fast.)
    2. Second, wash skin with water. (Water temperature does not matter; if you're outside, it's likely only cold water will be available.)
    3. Third, take a regular shower with soap and warm water. Do not use soap before this point because soap will tend to pick up some of the urushiol from the surface of the skin and move it around
    4. Clothes, shoes, tools, and anything else that may have been in contact with the urushiol should be wiped off with alcohol and water. Clothing should be washed in hot soapy water. The oil from these plants can remain on surfaces for days or weeks.(5) Be sure to wear gloves or otherwise cover your hands while doing this and then discard the hand covering.
    5. If you think a pet has been near an area with poison ivy, oak, or sumac, bathe the animal in warm, soapy water. Wear long sleeves and rubber gloves to avoid getting the oil on your skin. Discard the gloves when done and wash the long-sleeve shirt in hot soapy water.(5)

References

(1) Outsmarting Poison Ivy and It's Cousins from the FDA
(2) Allergy: Poison Ivy, Oak and Sumac from eMedicine.com
(3)
Plant Poisoning: Toxicodendron from eMedicine.com
(4)
Poison Ivy, Poison Oak and Poison Sumac from Merck Source
(5)
Poison Plants from the Asthma and Allergy Foundation
(6)
Michigan State University, Poison Ivy Control
(7) Virginia Creeper, from the USDA

--Written by N Thompson, ARNP in collaboration with C Thompson and M Thompson, MD, Internal Medicine, Last updated July 2008

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Leaves of 3, let it be! This is an up-to-date educational source for poison ivy, oak, and sumac. Health care providers may feel free to print out copies for their patient's use. Please note that content may not be copied for resale or other commercial use such as for web sites. The content on this site is for informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment.   
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