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      • Poison ivy is a type of allergenic plant in the genus Toxicodendron native to Asia and North America. Formerly considered a single species, Toxicodendron radicans, poison ivies are now generally treated as a complex of three separate species: T. radicans, T. rydbergii, and T. orientale. They are well known for causing urushiol-induced contact dermatitis, an itchy, irritating, and sometimes painful rash, in most people who touch them. The rash is caused by urushiol, a clear liquid compound in the plant's sap. They are variable in appearance and habit, and despite its common name, it is not a "true" ivy (Hedera), but rather a member of the cashew and pistachio family (Anacardiaceae). T. radicans is commonly eaten by many animals, and the seeds are consumed by birds, but poison ivy is most often thought of as an unwelcome weed.


      Species


      Three species of poison ivy are generally recognised; they are sometimes considered subspecies of Toxicodendron radicans:

      Toxicodendron orientale: found in East Asia.
      Toxicodendron radicans: found throughout eastern Canada and the United States, Mexico and Central America, Bermuda and the Bahamas.
      Toxicodendron rydbergii: found throughout Canada and much of the United States except the southeast.


      Description


      Poison ivies can grow as small plants, shrubs, or climbing vines. They are commonly characterized by clusters of leaves, each containing three leaflets, hence the common expression "leaves of three, let it be". These leaves can vary between an elliptic to egg shape and will have either smooth, lobed, or toothed margins. Additionally, the leaf clusters are alternate on the stem. Clusters of small, greenish flowers bloom from May to July and produce white berries in the fall a few millimeters in diameter.



















      Health effects



      Urushiol-induced contact dermatitis is the allergic reaction caused by poison ivy. In extreme cases, a reaction can progress to anaphylaxis. Around 15 to 25 percent of people have no allergic reaction to urushiol, but most people have a greater reaction with repeated or more concentrated exposure.
      Over 350,000 people are affected by urushiol annually in the United States.
      The oozing fluids released by scratching blisters do not spread the poison. The fluid in the blisters is produced by the body and it is not urushiol itself. The appearance of a spreading rash indicates that some areas received more of the poison and reacted sooner than other areas or that contamination is still occurring from contact with objects to which the original poison was spread.
      Those affected can unknowingly spread the urushiol inside the house, on phones, door knobs, couches, counters, desks, and so on, thus in fact repeatedly coming into contact with poison ivy and extending the length of time of the rash. If this happens, the surfaces should be wiped with bleach or a commercial urushiol removal agent. The blisters and oozing result from blood vessels that develop gaps and leak fluid through the skin; if the skin is cooled, the vessels constrict and leak less. If plant material with urushiol is burned and the smoke then inhaled, this rash will appear on the lining of the lungs, causing extreme pain and possibly fatal respiratory difficulty. If poison ivy is eaten, the mucus lining of the mouth and digestive tract can be damaged.
      Urushiol oil can remain active for several years, so handling dead leaves or vines can cause a reaction. In addition, oil transferred from the plant to other objects (such as pet fur) can cause the rash if it comes into contact with the skin. Clothing, tools, and other objects that have been exposed to oil should be washed to prevent further reactions.


      = Treatment

      =

      Immediate washing with soap and cold water or rubbing alcohol may help prevent a reaction. During a reaction, calamine lotion or diphenhydramine may help mitigate symptoms. Corticosteroids, either applied to the skin or taken by mouth, may be appropriate in extreme cases. An astringent containing aluminum acetate (such as Burow's solution) may also provide relief and soothe the uncomfortable symptoms of the rash.
      Urushiol binds to the skin on contact where it causes severe itching that develops into reddish inflammation or uncoloured bumps, and then blistering. These lesions may be treated with calamine lotion, Burow's solution compresses, dedicated commercial poison ivy itch creams, or baths to relieve discomfort, though recent studies have shown some traditional medicines to be ineffective. Over-the-counter products to ease itching—or simply oatmeal baths and baking soda—are now recommended by dermatologists for the treatment of poison ivy.
      A plant-based remedy cited to counter urushiol-induced contact dermatitis is jewelweed, though jewelweed extracts had no positive effect in clinical studies. Others argue that prevention of lesions is easy if one practices effective washing, using plain soap, scrubbing with a washcloth, and rinsing three times within 2–8 hours of exposure.
      The pentadecyl catechols of the oleoresin within the sap of poison ivy and related plants causes the allergic reaction; the plants produce a mixture of pentadecylcatechols, which collectively is called urushiol. After injury, the sap leaks to the surface of the plant where the urushiol becomes a blackish lacquer after contact with oxygen.


      Prognosis


      Typically, the rash from the urushiol oil lasts about five to twelve days, but in extreme cases it can last a month or more. A urushiol rash usually develops within a week of exposure and can last 1–4 weeks, depending on severity and treatment. In rare cases, urushiol reactions may require hospitalization.


      = Related species

      =
      People who are sensitive to urushiol can also experience a similar rash from mangoes. Mangoes are in the same family (Anacardiaceae) as poison ivy; the sap of the mango tree and skin of mangoes has a chemical compound similar to urushiol. A related allergenic compound is present in the raw shells of cashews. Similar reactions have been reported occasionally from contact with the related fragrant sumac (Rhus aromatica) and Japanese lacquer tree. These other plants are also in the family Anacardiaceae.


      Similar allergenic plants


      Gluta spp (rengas tree)
      Lithraea molleoides (aruera – South America)
      Smodingium argutum (African poison ivy)
      Toxicodendron pubescens (poison oak – eastern)
      Toxicodendron diversilobum (poison oak – western)
      Toxicodendron vernix (poison sumac)
      Toxicodendron vernicifluum (Japanese lacquer tree)


      References




      External links


      Site with extensive photo images of plants and skin rashes

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    Poison ivy - Wikipedia

    Poison ivy is a type of allergenic plant in the genus Toxicodendron native to Asia and North America. Formerly considered a single species, Toxicodendron radicans, poison ivies are now generally treated as a complex of three separate species: T. …

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    07 Mei 2020 · We'll show you how to identify poison ivy during the spring, summer, fall, and winter.

    Poison ivy rash - Symptoms and causes - Mayo Clinic

    15 Mei 2024 · Poison ivy rash is caused by an allergic reaction to an oily resin called urushiol (u-ROO-she-ol). This oil is in the leaves, stems and roots of poison ivy, poison oak and poison sumac. Wash your skin right away if you come into contact with this oil, unless you know you're not sensitive to it.

    Poison Ivy Rash: Pictures, Symptoms, and Treatment - Healthline

    12 Mar 2024 · Poison ivy can be found in nearly every state, so there’s a good chance you will eventually cross paths with it. See pictures and learn about remedies.

    Poison Ivy Rash: How To Identify, Symptoms, Causes - Health

    19 Apr 2024 · Poison ivy is a poisonous plant that can cause a skin rash in people who come into contact with its leaves, stems, or roots. The medical name for this rash is contact dermatitis or Rhus...

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    15 Mei 2024 · You probably won't need medical treatment for a poison ivy rash unless it spreads widely, persists for more than a few weeks or becomes infected. If you're concerned, you'll …

    Poison Ivy, Poison Oak and Poison Sumac - Cleveland Clinic

    A poison ivy rash on your skin usually looks like red, itchy bumps. Some people can develop black spots or streaks on their skin instead of the telltale red rash (this is rare).

    Poison Ivy, Oak, and Sumac Rash - Johns Hopkins Medicine

    Poison ivy, poison oak, and poison sumac are plants that cause an allergic rash in most people who touch them. The rash is caused by a reaction to an oil in the plants called urushiol.

    Poison Ivy: Diagnosis, Treatment, and When to Seek Help - Poison …

    The poison ivy vine will often produce yellow-green flowers and white or off-white berries in the spring and early fall. Its spring shoots are often red, and its leaves turn red or yellow in the fall.

    Poison Ivy - University of Maryland Extension

    18 Sep 2023 · Poison ivy, Toxicodendron radicans, is a common native plant found in woodlands, fields, pastures, farms, and home landscapes. In natural areas, its berries provide nutritious food for migrating birds.