Toxicodendron radicans

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Poison ivy
Toxicodendron radicans or poison ivy
Ground-level poison ivy, Ottawa, Ontario
Scientific classification
Kingdom:Plantae
(unranked):Angiosperms
(unranked):Eudicots
(unranked):Rosids
Order:Sapindales
Family:Anacardiaceae
Genus:Toxicodendron
Species:T. radicans
Binomial name
Toxicodendron radicans
(L.) Kuntze
Synonyms
  • Rhus toxicodendron
  • Rhus radicans
 
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Poison ivy
Toxicodendron radicans or poison ivy
Ground-level poison ivy, Ottawa, Ontario
Scientific classification
Kingdom:Plantae
(unranked):Angiosperms
(unranked):Eudicots
(unranked):Rosids
Order:Sapindales
Family:Anacardiaceae
Genus:Toxicodendron
Species:T. radicans
Binomial name
Toxicodendron radicans
(L.) Kuntze
Synonyms
  • Rhus toxicodendron
  • Rhus radicans

Toxicodendron radicans, commonly known as poison ivy (older synonyms are Rhus toxicodendron and Rhus radicans),[1] is a poisonous North American and Asian plant that is well known for its production of urushiol, a clear liquid compound in the sap of the plant that causes an itching, irritation and sometimes painful rash in most people who touch it.[2] The plant is not a true ivy (Hedera).

Poison ivy can be found growing in any of the following forms:

Distribution and habitat[edit]

Poison ivy grows throughout much of North America, including the Canadian Maritime provinces, Quebec, Ontario, Manitoba, and all U.S. states east of the Rocky Mountains, as well as in the mountainous areas of Mexico up to around 1,500 m (4,900 ft) (caquistle or caxuistle is the Nahuatl term[clarification needed] ). It is normally found in wooded areas, especially along edge areas where the tree line breaks and allows sunshine to filter through. It also grows in exposed rocky areas, open fields and disturbed areas.

It may grow as a forest understory plant, although it is only somewhat shade tolerant.[1] The plant is extremely common in suburban and exurban areas of New England, the Mid-Atlantic, and southeastern United States. Similar species, poison oak, and Toxicodendron rydbergii are found in western North America. Poison ivy rarely grows at altitudes above 1,500 m (4,900 ft), although the altitude limit varies in different locations.[1] The plants can grow as a shrub up to about 1.2 metres (3.9 ft) tall, as a groundcover 10–25 cm (3.9–9.8 in) high, or as a climbing vine on various supports. Older vines on substantial supports send out lateral branches that may be mistaken for tree limbs at first glance.

It grows in a wide variety of soil types, and soil pH from 6.0 (acidic) to 7.9 (moderately alkaline). It is not particularly sensitive to soil moisture, although it does not grow in desert or arid conditions. It can grow in areas subject to seasonal flooding or brackish water. [1]

It is more common now than when Europeans first arrived in North America. The development of real estate adjacent to wild, undeveloped land has engendered "edge effects," enabling poison ivy to form vast, lush colonies in these areas. It is listed as a noxious weed in the U.S. states of Minnesota and Michigan, and the Canadian province of Ontario.

Outside North America, poison ivy is also found in the temperate parts of Asia, in Japan, Taiwan, the Russian islands of Sakhalin and the Kuriles, and in parts of China.[3]

A study by researchers at the University of Georgia found that poison ivy is particularly sensitive to CO2 levels, greatly benefiting from higher CO2 in the atmosphere. Poison ivy's growth and potency has already doubled since the 1960s, and it could double again once CO2 levels reach 560 ppm.[4]

Description[edit]

Poison ivy vine with typical reddish "hairs" (like leaves, vines are extremely poisonous to humans)

The deciduous leaves of poison ivy are trifoliate with three almond-shaped leaflets.[1] Leaf color ranges from light green (usually the younger leaves) to dark green (mature leaves), turning bright red in fall; though other sources say leaves are reddish when expanding, turn green through maturity, then back to red, orange, or yellow in the fall. The leaflets of mature leaves are somewhat shiny. The leaflets are 3–12 cm (1.2–4.7 in) long, rarely up to 30 cm (12 in). Each leaflet has a few or no teeth along its edge, and the leaf surface is smooth. Leaflet clusters are alternate on the vine, and the plant has no thorns. Vines growing on the trunk of a tree become firmly attached through numerous aerial rootlets.[5] The vines develop adventitious roots, or the plant can spread from rhizomes or root crowns. The milky sap of poison ivy darkens after exposure to the air.

Poison ivy spreads either vegetatively or sexually. Poison ivy is dioecious; flowering occurs from May to July. The yellowish- or greenish-white flowers are typically inconspicuous and are located in clusters up to 8 cm (3.1 in) above the leaves. The berry-like fruit, a drupe, mature by August to November with a grayish-white colour.[1] Fruits are a favorite winter food of some birds and other animals. Seeds are spread mainly by animals and remain viable after passing through the digestive tract.

Aids to identification[edit]

Poison ivy leaf and berries

The following four characteristics are sufficient to identify poison ivy in most situations: (a) clusters of three leaflets, (b) alternate leaf arrangement, (c) lack of thorns, and (d) each group of three leaflets grows on its own stem, which connects to the main vine.

The appearance of poison ivy can vary greatly between environments, and even within a single area. Identification by experienced people is often made difficult by leaf damage, the plant's leafless condition during winter, and unusual growth forms due to environmental or genetic factors.

Various mnemonic rhymes describe the characteristic appearance of poison ivy:[6]

  1. "Leaflets three; let it be" is the best known and most useful cautionary rhyme. It applies to poison oak, as well as to poison ivy.
  2. "Hairy vine, no friend of mine."[7]
  3. "Longer middle stem, stay away from them." This refers to the middle leaflet having a visibly longer stem than the two side leaflets and is a key to differentiating it from the similar-looking Rhus aromatica (fragrant sumac).
  4. "Raggy rope, don't be a dope!" Poison ivy vines on trees have a furry "raggy" appearance. This rhyme warns tree climbers to be wary. Old, mature vines on tree trunks can be quite large and long, with the recognizable leaves obscured among the higher foliage of the tree.[8]
  5. "One, two, three? Don't touch me."
  6. "Berries white, run in fright" and "Berries white, danger in sight."[9]
  7. "Red leaflets in the spring, it's a dangerous thing." This refers to the red appearance that new leaflets sometimes have in the spring. (Note that later, in the summer, the leaflets are green, making them more difficult to distinguish from other plants, while in autumn they can be reddish-orange.)
  8. "Side leaflets like mittens, will itch like the dickens." This refers to the appearance of some, but not all, poison ivy leaves, where each of the two side leaflets has a small notch that makes the leaflet look like a mitten with a "thumb." (Note that this rhyme should not be misinterpreted to mean that only the side leaflets will cause itching, since actually all parts of the plant can cause itching.)
  9. "If it's got hair, it won't be fair." This refers to the hair that can be on the stem and leaves of poison ivy.

Effects on the body[edit]

Urushiol-induced contact dermatitis is the allergic reaction caused by poison ivy. In extreme cases, a reaction can progress to anaphylaxis. Around 15% to 30% of people have no allergic reaction.[10][11] Most people will become sensitized with repeated or more concentrated exposure to urushiol.[10]

Over 350,000 people are affected by poison ivy annually in the US.[12]

The pentadecylcatechols 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.[2][13]

Poison ivy on a roadside

Urushiol binds to the skin on contact, where it causes severe itching that develops into reddish coloured inflammation or non-coloured bumps, and then blistering. These lesions may be treated with Calamine lotion, Burow's solution compresses or baths to relieve discomfort,[14] though recent studies have shown some traditional medicines to be ineffective.[15][16] 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.[17] A plant based remedy cited to counter urushiol induced contact dermatitis is jewelweed. "The results of a clinical study, in which a 1:4 jewelweed preparation was compared for its effectiveness with other standard poison ivy dermatitis treatments was published in 1958 (Annals of Allergy 1958;16:526-527). Of 115 patients treated with jewelweed, 108 responded ‘most dramatically to the topical application of this medication and were entirely relieved of their symptoms within 2 or 3 days after the institution of treatment.' It was concluded that jewelweed is an excellent substitute for ACTH and the corticosteroids in the treatment of poison ivy dermatitis.[18] However, other sources have since concluded that jewelweed is ineffective or of questionable effectiveness. [19][20][21][22]

Blisters from contact with poison ivy

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.[23] 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. 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.[citation needed] If poison ivy 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.[24] If poison ivy is eaten, the mucus lining of the mouth and digestive tract can be damaged.[25] A poison ivy rash usually develops within a week of exposure and can last anywhere from one to four weeks, depending on severity and treatment. In rare cases, poison ivy reactions may require hospitalization.[26]

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.[27][28] Clothing, tools, and other objects that have been exposed to the oil should be washed to prevent further transmission.

People who are sensitive to poison ivy 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.[29] A related allergenic compound is present in the raw shells of cashews.[30] 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 Anacardiaceae family.

Treatment of poison ivy rash[edit]

See Wikipedia section on urushiol-induced contact dermatitis - treatments.

Immediate washing with soap and 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.

Similar-looking plants[edit]

See also[edit]

References[edit]

  1. ^ a b c d e f USDA Fire Effects Information System: SPECIES: Toxicodendron radicans, T. rydbergii
  2. ^ a b Donald G. Barceloux (2008). Medical Toxicology of Natural Substances: Foods, Fungi, Medicinal Herbs, Plants, and Venomous Animals. John Wiley and Sons. pp. 681–. ISBN 978-0-471-72761-3. Retrieved 26 July 2010. 
  3. ^ "Toxicodendron radicans - Distribution Range". www.ars-grin.gov. Retrieved 7 April 2013. 
  4. ^ David Templeton (July 22, 2013). "Climate change is making poison ivy grow bigger and badder". Pittsburgh Post-Gazette. Retrieved July 23, 2013. 
  5. ^ Petrides, George A. A Field Guide to Trees and Shrubs (Peterson Field Guides), Boston: Houghton Mifflin Co., 1986, p. 130.
  6. ^ "Poison Ivy Treatment Guide , Getting Rid of the Plants: Identifying Poison Ivy". 
  7. ^ http://www.parks.ca.gov/pages/735/files/transcriptmtlivermoreangelisland.pdf Page 3.
  8. ^ Poison Ivy
  9. ^ Kamp Krusty
  10. ^ a b Howstuffworks "How Poison Ivy Works"
  11. ^ Contact-Poisonous Plants of the World
  12. ^ Chaker, Anne Marie; Athavaley, Anjali (June 22, 2010). "Least-Welcome Sign of Summer". The Wall Street Journal. p. D1. 
  13. ^ Robert L. Rietschel; Joseph F. Fowler; Alexander A. Fisher (2008). Fisher's contact dermatitis. PMPH-USA. pp. 408–. ISBN 978-1-55009-378-0. Retrieved 26 July 2010. 
  14. ^ Wilson, W. H. & Lowdermilk, P. (2006). Maternal Child Nursing Care (3rd edition). St. Louis: Mosby Elsevier.
  15. ^ "American Topics. An Outdated Notion, That Calamine Lotion". Archived from the original on 2007-06-19. Retrieved 2007-07-19. 
  16. ^ Appel, L.M. Ohmart and R.F. Sterner, Zinc oxide: A new, pink, refractive microform crystal. AMA Arch Dermatol 73 (1956), pp. 316–324. PMID 13301048
  17. ^ "American Academy of Dermatology - Poison Ivy, Oak & Sumac". 
  18. ^ Tyler’s Herbs of Choice: The Therapeutic Use of Phytomedicinals. Varro Tyler, PhD. ISBN 978-0789028099
  19. ^ D. Long, N. H. Ballentine, J. G. Marks. Treatment of poison ivy/oak allergic contact dermatitis with an extract of jewelweed. Am. J. Contact. Dermat. 8(3):150-3 1997 PMID 9249283
  20. ^ Gibson, MR; Maher, FT (1950). "Activity of jewelweed and its enzymes in the treatment of Rhus dermatitis.". Journal of the American Pharmaceutical Association. American Pharmaceutical Association 39 (5): 294–6. PMID 15421925. 
  21. ^ J. D. Guin, R. Reynolds. Jewelweed treatment of poison ivy dermatitis. Contact Dermatitis 6(4):287-8 1980 PMID 6447037, doi:10.1111/j.1600-0536.1980.tb04935.x
  22. ^ Zink, B. J.; Otten, E. J.; Rosenthal, M.; Singal, B. (1991). "The effect of jewel weed in preventing poison ivy dermatitis.". Journal of Wilderness Medicine 2 (3): 178–182. doi:10.1580/0953-9859-2.3.178. 
  23. ^ "Facts about Poison Ivy: Is it contagious?". 
  24. ^ "Facts about Poison Ivy: How do you get poison ivy?". 
  25. ^ Robert Alan Lewis (1998). Lewis' dictionary of toxicology. CRC Press. pp. 901–. ISBN 978-1-56670-223-2. Retrieved 18 August 2010. 
  26. ^ "Facts about Poison Ivy: How long does the rash last?, What can you do once the itching starts?, How do you get poison ivy?". 
  27. ^ Poison Ivy, Oak & Sumac
  28. ^ "Facts about Poison Ivy: How do you get poison ivy?, Pets and Poison Ivy, How long does the oil last?". 
  29. ^ Mangos and Poison Ivy (New England Journal of Medicine Web Article)
  30. ^ Rosen, T.; Fordice, D. B. (April 1994). "Cashew Nut Dermatitis". Southern Medical Journal 87 (4): 543–546. doi:10.1097/00007611-199404000-00026. PMID 8153790. Retrieved 2011-01-13. 

External links[edit]