Urushiol-induced contact dermatitis 2467826 225609832 2008-07-14T15:21:58Z NJGW 6012605 /* Mechanism */ ce {{Infobox_Disease | Name = Urushiol-induced contact dermatitis | Image = | Caption = | DiseasesDB = 32755 | ICD10 = {{ICD10|L|23|7|l|20}} | ICD9 = {{ICD9|692.6}} | ICDO = | OMIM = | MedlinePlus = | eMedicineSubj = emerg | eMedicineTopic = 452 | MeshID = D011040 | }} [[Image:Poisonoak.jpg|thumb|233px|right|''Toxicodendron pubescens'' ("Atlantic Poison-oak"), one of a large number of species containing urushiol irritants.]] [[Image:URUSHIOL BLISTERING.jpg|thumb|233px|Blistering 48 hours after urushiol contact]] [[Image:Poisonivyrash.jpg|thumb|233px|Poison ivy rash after 2 days.]] '''Urushiol-induced contact dermatitis''' (also called '''Toxicodendron dermatitis''' and '''Rhus dermatitis''') is the medical name given to [[allergy|allergic]] [[rash]]es produced by oil [[urushiol]], which is contained in various plants, including the plants of the genus ''[[Toxicodendron]]'' (including [[poison ivy]], [[Toxicodendron diversilobum|poison oak]], and [[poison Sumac]]), as well as other plants in the family [[Anacardiaceae]] ([[mango]], [[Rengas tree]], [[Burmese lacquer tree]], [[India marking nut tree]], and the shell of the [[cashew]] nut), and even unrelated plants such as ''[[Ginkgo biloba]]''. Symptoms of the rash 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 U.S., while poison-ivy is most rampant in the eastern U.S.. Dermatitis from [[poison sumac]] is less common, but just as problematic. ==Exposure== Urushiol-induced contact dermatitis is contracted by contact with a plant or any other object containing urushiol oil. The oil adheres to almost anything it comes in contact with, such as towels, blankets, even clothing. Clothing or other materials that contact the plant and then, before being washed, contact the skin are common causes of exposure. Normally, it takes about 24 hours for the rash to first appear, though it may worsen during the next few days and may appear to spread, when in fact what is happening is that areas that received a lesser dose are reacting. The rash can take one to two weeks to run its course, and in some cases up to five weeks. Urushiol is primarily found in the spaces between plant cells beneath the outer skin of the plant, so the effects of urushiol rash 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 spread once it has bound with the skin, and it is not found in weeping blisters. Although simple skin exposure is most common, ingestion can also lead to serious, more systemic reactions. Burning plant material is commonly said to create urushiol-laden smoke that causes systemic reaction as well as rash inside the throat and on the eyes. A high-temperature fully inflamed bonfire might incinerate the urushiol before it can cause harm, while a smoldering fire could vaporize the volatile oil and spread it as white smoke. However, some sources dispute the danger of burning urushiol-containing plant material.<ref>{{cite book |title=A Colour Atlas of Poisonous Plants: A Handbook for Pharmacists, Doctors, Toxicologists, and Biologists |author=Dietrich Frohne and Hans Jurgen Pfander |year=1984 |pages=291 pp. |publisher=Wolfe Publishing Ltd |isbn=0-7234-0839-4}}</ref> ==Mechanism== The toxic effects of [[urushiol]] are largely indirect, mediated by an induced [[autoimmune]] response. [[Urushiol]] chemically reacts with, binds to and changes the shape of [[integral membrane protein]]s on exposed skin cells. Affected proteins interfere with the immune system's ability to recognize these cells as normal parts of the body (perhaps causing the immune system to mistake them for invading parasites), causing a [[T-cell]] mediated [[immune response]]. This immune response is directed towards the complex of urushiol derivatives bound in the skin proteins, attacking the cells as if they were foreign bodies. ==Rash== The result is an allergic [[eczema]]tous [[contact dermatitis]] characterized by redness, swelling, [[papule]]s, [[vesicle]]s, [[blister]]s, and streaking. People vary greatly in their sensitivity to urushiol. In approximately 15%<ref>[http://science.howstuffworks.com/poison-ivy.htm Howstuffworks "How Poison Ivy Works"]</ref> to 30%<ref>[http://mic-ro.com/plants/ Contact-Poisonous Plants of the World]</ref> of people urushiol does not initiate an immune system response, while at least 25% of people have very strong immune responses resulting in severe symptoms. Since the skin reaction is an allergic one, people may develop progressively stronger reactions after repeated exposures, or show no immune response on their first exposure, but show sensitivity on following exposures. People of significant Native American ancestry rarely are affected by urushiol and display a heritable resistance to it due to living in North America under selective pressure from Poison Ivy and Poison Oak for many millennia.{{Fact|date=June 2008}} The rash takes one to two weeks to run its course, but normally does not leave scars. Severe cases will have small (1–2 mm) clear fluid-filled blisters on the skin. Pus-filled vesicles, containing a whitish fluid, may indicate a secondary infection. Most poison ivy rashes, without infections, will self-resolve within 14 days without treatment. Excessive scratching may result in secondary [[infection]], commonly by [[staphylococcus|staphylococcal]] and [[streptococcus|streptococcal]] species. These may require the use of [[antibiotics]]. ==Treatments== Primary treatment involves washing exposed skin thoroughly with soap and water as soon as possible after exposure is discovered. Soap or detergent is necessary, as urushiol is a [[hydrophobic]] (not water-soluble) oil. Commercial removing preparations which are available in areas where poison-ivy grows usually contain [[surfactant]]s such as the nonionic [[detergent]] [[Triton X-100]] to solubilize urushiol. Some preparations additionally contain [[scrubbing particle]]s. [[Antihistamine]]s and [[hydrocortisone]] creams or antihistamines by mouth in severe cases can be used to alleviate the symptoms of a developed rash. No vaccine has been developed to counter urushiol symptoms, so the most effective "cures" are generally held to be those products that physically remove the urushiol. After about 15 minutes of exposure, the urushiol is chemically bonded to the skin and can only be removed with pharmaceutical products, which vary by person in effectiveness.{{Fact|date=April 2008}} In cases of extreme symptoms, steroids such as [[Prednisone]] are sometimes administered to attenuate the immune response. If bacterial secondary infection of affected areas occurs, antibiotics may also be necessary. There are many [[home remedy|home remedies]] that deal with treating urushiol rashes. Most have been discredited, but persist despite their falsehood. Some clarifications (these statements are true): * Scrubbing with plain soap and cold water will remove the urushiol from skin if it is done within a few minutes of exposure, before it bonds * Ordinary laundering with laundry detergent will remove urushiol from most clothing, but not from leather or suede * The fluid from the resulting blisters does '''not''' spread poison ivy to others * Poison ivy is '''not''' harmless when the leaves have fallen off as the toxic resin is very persistent. Every part of the plant contains urushiol, and can cause a rash with exposure at any time of the year * Ice, water, soap, lotions, dry cold air, do '''not''' help cure poison-ivy rashes, they only soothe the itch * Urinating on the affected areas has '''no''' effect * [[Burow's solution]], [[calamine lotion]] and [[Jewelweed]] are ineffective or of questionable effectiveness against itching == See also == * [[Anti-itch drug]] * [[Toxin]] ==References== <references/> ==External links== * [http://www.intelihealth.com/IH/ihtIH/WSIHW000/7945/8214/7770.html?d=dmtJHE%20 Poison Ivy: Prevention and Treatment] * [http://paipm.cas.psu.edu/279.htm Poison Ivy Myths] * [http://waynesword.palomar.edu/ww0802.htm Poison Oak] at ''Wayne's Word'' * {{DermAtlas|-1892628434}} {{Diseases of the skin and subcutaneous tissue}} [[Category:Dermatology]] [[Category:Wood-finishing techniques]] [[es:Dermatitis de contacto por urushiol]]