Urushiol-induced contact dermatitis

Urushiol-induced contact dermatitis (also called Toxicodendron dermatitis or Rhus dermatitis) is a type of allergic contact dermatitis caused by the oil urushiol found in various plants, most notably species of the genus Toxicodendron: poison ivy, poison oak, poison sumac, and the Chinese lacquer tree. The name is derived from the Japanese word for the sap of the Chinese lacquer tree, urushi. Other plants in the sumac family (including mango, pistachio, the Burmese lacquer tree, the India marking nut tree, and the shell of the cashew) also contain urushiol,[1] as do unrelated plants such as Ginkgo biloba.[2]

Urushiol-induced contact dermatitis
Poison ivy contact dermatitis.jpg
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As is the case with all contact dermatitis, urushiol-induced allergic rashes are a Type IV hypersensitivity reaction, also known as delayed-type hypersensitivity. Symptoms include itching, inflammation, oozing, and, in severe cases, a burning sensation.

The American Academy of Dermatology estimates that there are up to 50 million cases of urushiol-induced dermatitis annually in the United States alone, accounting for 10% of all lost-time injuries in the United States Forest Service. Poison oak is a significant problem in the rural Western and Southern United States, while poison ivy is most rampant in the Eastern United States. Dermatitis from poison sumac is less common.

Signs and symptomsEdit

Urushiol causes an eczematous contact dermatitis characterized by redness, swelling, papules, vesicles, blisters, and streaking.[3] People vary greatly in their sensitivity to urushiol. In approximately 15%[4] to 30%[5] of people, urushiol does not trigger an immune system response, while at least 25% of people have a very strong immune response resulting in severe symptoms. Since the skin reaction is an allergic one, people may develop progressively stronger reactions after repeated exposures, or have no immune response on their first exposure but show sensitivity on subsequent exposures.[citation needed]

Approximately 80% to 90% of adults will get a rash if they are exposed to 50 micrograms of purified urushiol. Some people are so sensitive that it only takes a trace of urushiol (two micrograms, or less than one ten-millionth of an ounce) on the skin to initiate an allergic reaction.[6]

The rash takes one to two weeks to run its course and may cause scars, depending on the severity of the exposure. Severe cases involve small (1–2 mm), clear, fluid-filled blisters on the skin. Pus-filled vesicles containing a whitish fluid may indicate an infection. Most poison ivy rashes, without infections, will resolve within 14 days without treatment. Excessive scratching may result in infection, commonly by staphylococcal and streptococcal species; these may require antibiotics.


Toxicodendron pubescens (Atlantic poison oak), one of a large number of species containing urushiol irritants.

Urushiol-induced contact dermatitis is caused by contact with a plant or any other object containing urushiol oil. The oil adheres to almost anything with which it comes in contact, such as towels, blankets, clothing, and landscaping tools. Clothing or other materials that touch the plant and then, before being washed, touch the skin are common causes of exposure.

For people who have never been exposed or are not yet allergic to urushiol, it may take 10 to 21 days for a reaction to occur the first time. Once allergic to urushiol, however, most people break out 48 to 72 hours after contact with the oil. Typically, individuals have been exposed at least once, if not several times, before they develop a rash.[7] The rash typically persists one to two weeks, but in some cases may last up to five weeks.

Urushiol is primarily found in the spaces between cells beneath the outer skin of the plant, so the effects are less severe if the plant tissue remains undamaged on contact. Once the oil and resin are thoroughly washed from the skin, the rash is not contagious. Urushiol does not always spread once it has bonded with the skin, and cannot be transferred once the urushiol has been washed away.

Although simple skin exposure is most common, ingestion of urushiol can lead to serious, systemic reactions. Burning plant material is commonly said to create urushiol-laden smoke that causes a systemic reaction, as well as a rash in the throat and eyes. Firefighters often get rashes and eye inflammation from smoke-related contact.[8] A high-temperature bonfire may incinerate urushiol before it can cause harm, while a smoldering fire may vaporize the volatile oil and spread it as white smoke. However, some sources dispute the danger of burning urushiol-containing plant material.[9]


A video describing the mechanism of action for poison ivy and other plants containing urushiol.

Urushiols are oxidized in-vivo, generating a quinone form of the molecules.[10][non-primary source needed] The toxic effect is indirect, mediated by an induced immune response. The oxidized urushiols act as haptens, chemically reacting with, binding to, and changing the shape of integral membrane proteins on exposed skin cells. Affected proteins interfere with the immune system's ability to recognize these cells as normal parts of the body, causing a T-cell-mediated immune response.[11] This response is directed at the complex of urushiol derivatives (namely, pentadecacatechol) bound in the skin proteins, attacking the cells as if they were foreign bodies.


Treatment consists of two phases: stopping the urushiol contact that is causing the reaction (this must be done within minutes)[12] and, later, reducing the pain and/or itching.[6][13]

Primary treatment involves washing exposed skin thoroughly with soap, cool water, and friction as soon as possible after exposure is discovered. Soap or detergent is necessary because urushiol is an oil; friction, with a washcloth or something similar, is necessary because urushiol adheres strongly to the skin.[14] Commercial removal preparations, which are available in areas where poison ivy grows, usually contain surfactants, such as the nonionic detergent Triton X-100, to solubilize urushiol; some products also contain abrasives.

The U.S. Food and Drug Administration recommends applying a wet compress or soaking the affected area in cool water; topical corticosteroids (available over-the-counter) or oral corticosteroids (available by prescription); and topical skin protectants, such as zinc acetate, zinc carbonate, zinc oxide, and calamine. Baking soda or colloidal oatmeal can relieve minor irritation and itching. Aluminium acetate, sometimes known as Burow's solution, can also ease the rash.[15]

Showers or compresses using hot (but not scalding) water can relieve itching for up to several hours, though this "also taxes the skin's integrity, opening pores and generally making it more vulnerable", and is only useful for secondary treatment (not for cleaning urushiol from the skin, which should be done with cold water).[16] People who have had a prior systemic reaction may be able to prevent subsequent exposure from turning systemic by avoiding heat and excitation of the circulatory system and applying moderate cold to any infected skin with biting pain.

Antihistamine creams, or oral antihistamines, do not alleviate the itching of a developed urushiol-induced contact rash. This is because of the underlying histamine-independent physiology of a Type IV hypersensitivity reaction. The sleepiness that first generation oral antihistamines (i.e., diphenhydramine and other first generation H1 antagonists) produce may help people ignore the itch during the night, but do not stop nighttime scratching and may actually decrease overall sleep quality.[17]

In cases of extreme symptoms, steroids such as prednisone, triamcinolone, or dexamethasone are sometimes administered to attenuate the immune response and prevent long-term skin damage, especially if the eyes are involved. Prednisone is the most commonly prescribed systemic treatment but can cause serious adrenal suppression, so it must be taken carefully and tapered off slowly.[18] If bacterial secondary infection of affected areas occurs, antibiotics may also be necessary.

Scrubbing with plain soap and cold water will remove urushiol from skin if it is done within a few minutes of exposure.[12] Many home remedies and commercial products (e.g., Tecnu, Zanfel) also claim to prevent urushiol rashes after exposure. A study that compared Tecnu ($1.25/oz.) with Goop Hand Cleaner or Dial Ultra Dishwashing Soap ($0.07/oz.) found that differences among the three—in the range of 56–70% improvement over no treatment—were nonsignificant (P > 0.05), but that improvement over no treatment was significant at the same level of confidence.[19]

Further observationsEdit

  • Ordinary laundering with laundry detergent will remove urushiol from most clothing[20] but not from leather or suede.[citation needed]
  • Urushiol oil left on clothing and surfaces can be deactivated using bleach.[21]
  • The fluid from the resulting blisters does not spread urushiol to others.[22][23]
  • Blisters should be left unbroken during healing.[24]
  • Poison ivy and poison oak are still harmful when the leaves have fallen off, as the toxic residue is persistent, and exposure to any parts of plants containing urushiol can cause a rash at any time of the year.[12]
  • Ice, cold water, cooling lotions, and cold air do not help cure poison ivy rashes, but cooling can reduce inflammation and soothe the itch.[20][dead link]
  • Results for jewelweed as a natural agent for treatment are conflicting. Some studies indicate that it "failed to decrease symptoms of poison ivy dermatitis" [1980] and had "no prophylactic effect" [1997].[25] The juice of the leaves and stems of Impatiens capensis is a traditional Native American remedy for skin rashes, including poison ivy.[26] A peer-reviewed study in 2012 suggests the mechanism of action may be saponins in the plant acting in a manner similar to soap. The study further indicates soap is more effective and should be preferred if available.[27]


A rarely cited double-blind study in 1982 reported that a course of oral urushiol usually hyposensitized subjects, with the principal side effect, pruritus ani, being reported by 85% of the participants who ingested the urushiol.[28]

See alsoEdit


  1. ^ Gross, Michael; Baer, Harold; Fales, Henry M (1975). "Urushiols of poisonous anacardiaceae". Phytochemistry. 14 (10): 2263. doi:10.1016/S0031-9422(00)91113-0.
  2. ^ Lepoittevin, J.-P., Benezra, C., Asakawa, Y. 1989. Allergic contact dermatitis to Ginkgo biloba L.: relationship with urushiol. Arch. Dermatol. Res., 281: 227-230.
  3. ^ DermAtlas -1892628434
  4. ^ Wilson, Stephanie (2005-09-23). "Howstuffworks "How Poison Ivy Works"". Science.howstuffworks.com. Retrieved 2010-06-04.
  5. ^ Michael Rohde. "Contact-Poisonous Plants of the World". Mic-ro.com. Retrieved 2010-06-04.
  6. ^ a b "Poison Oak". Waynesword.palomar.edu. 2011-01-16. Retrieved 2015-10-06.
  7. ^ Ray, Thomas MD, Professor Emeritus of Dermatology. "Poison Ivy: The Most Common of Allergens". University of Iowa Health Care. Archived from the original on 12 January 2016. Retrieved 30 October 2015.
  9. ^ Dietrich Frohne; Hans Jurgen Pfander (1984). A Colour Atlas of Poisonous Plants: A Handbook for Pharmacists, Doctors, Toxicologists, and Biologists. Wolfe Publishing Ltd. p. 291 pp. ISBN 978-0-7234-0839-0.
  10. ^ Kalergis, Alexis M; López, Carolina B; Becker, Maria I; Diaz, Marisol I; Sein, Jorge; Garbarino, Juan A; De Ioannes, Alfredo E (Jan 1997). "Modulation of fatty acid oxidation alters contact hypersensitivity to urushiols: role of aliphatic chain beta-oxidation in processing and activation of urushiols". J Invest Dermatol. 108 (1): 57–61. doi:10.1111/1523-1747.ep12285632. PMID 8980288.
  11. ^ C.Michael Hogan (2008) Western poison-oak: Toxicodendron diversilobum, GlobalTwitcher, ed. Nicklas Stromberg "Archived copy". Archived from the original on 2009-07-21. Retrieved 2010-04-21.CS1 maint: archived copy as title (link)
  12. ^ a b c Bill Einsig, Bill (2002), Poison Ivy Myth: Science, Environment and Ecology Flash for Educators (No. 341), in Keystone Outdoors Magazine (May 11), excerpted by the Penn State Integrated Pest Management, accessed 7 October 2015.
  13. ^ "Soothing Remedies for Poison Ivy and Poison Oak". Googobits.com. 2005-08-04. Retrieved 2010-06-04.
  14. ^ "How to never have a serious poison ivy rash again" on YouTube
  15. ^ [1] Archived July 16, 2010, at the Wayback Machine
  16. ^ Hauser, Susan Carol; William L. Epstein (2008). A Field Guide to Poison Ivy, Poison Oak, and Poison Sumac. Globe Pequot. p. 60. ISBN 978-0-7627-4741-2. Retrieved 2010-11-21.
  17. ^ Prok, Lori. "Poison Ivy: Beyond the Basics". UpToDate. Retrieved 22 July 2020.
  18. ^ "Poison Ivy, Oak, and Sumac". Surviveoutdoors.com. Retrieved 2010-06-04.
  19. ^ Stibich, A. S.; Yagan, M.; Sharma, V.; Herndon, B. & Montgomery, C. (2001). "Cost-effective post-exposure prevention of poison ivy dermatitis". International Journal of Dermatology. 39 (7): 515–518. doi:10.1046/j.1365-4362.2000.00003.x. PMID 10940115. S2CID 2958342.
  20. ^ a b "Aetna InteliHealth: Featuring Harvard Medical School's Consumer Health Information". Intelihealth.com. Archived from the original on February 11, 2012. Retrieved 6 October 2015.
  21. ^ Chastant, Lisa Renee; Davis, Thomas; Libow, Lester (2018-01-16). "Black-spot poison ivy, a report of 3 cases with clinicopathologic correlation". JAAD Case Reports. 4 (2): 140–142. doi:10.1016/j.jdcr.2017.09.035. ISSN 2352-5126. PMC 5789763. PMID 29387766.
  22. ^ "Poison ivy, oak, and sumac". American Academy of Dermatology.
  23. ^ "Outsmarting Poison Ivy and Other Poisonous Plants". U.S. Food and Drug Administration. 16 August 2019.
  24. ^ "Poison Ivy, Oak and Sumac". OutDoorPlaces.com. Retrieved 22 September 2010.
  25. ^ Shenefelt, Philip D. (2011). "Herbal Treatment for Dermatologic Disorders". Herbal Medicine. Herbal Medicine: Biomolecular and Clinical Aspects. Oxidative Stress and Disease. 20115386 (2nd ed.). Boca Raton, Florida, USA: CRC Press. pp. 383–403. doi:10.1201/b10787-19. ISBN 9781439807132. PMID 22593930. Retrieved October 5, 2015.
  26. ^ Smith, Huron H., 1933, Ethnobotany of the Forest Potawatomi Indians, Bulletin of the Public Museum of the City of Milwaukee 7:1-230, page 42
  27. ^ Motz; Bowers; Young; Kinder (2012). "The effectiveness of jewelweed, Impatiens capensis, the related cultivar I. balsamina and the component, lawsone in preventing post poison ivy exposure contact dermatitis". Journal of Ethnopharmacology. 143 (1): 314–318. doi:10.1016/j.jep.2012.06.038. PMID 22766473.
  28. ^ Epstein, W. L.; Byers, V. S.; Frankart, W. (1982-09-01). "Induction of antigen specific hyposensitization to poison oak in sensitized adults". Archives of Dermatology. 118 (9): 630–633. doi:10.1001/archderm.1982.01650210010008. ISSN 0003-987X. PMID 06180687.

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