Urushiol
Encyclopedia
Urushiol is an oily organic allergen
found in plants of the family
Anacardiaceae
, especially Toxicodendron
spp. (e.g., poison oak
, poison ivy
, poison sumac
). It causes an allergic skin
rash on contact, known as urushiol-induced contact dermatitis
. The name comes from the Japanese
word Kiurushi which denotes a lacquer
produced in East Asia
from the sap of Toxicodendron vernicifluum (the Lacquer Tree). The oxidation and polymerization of urushiol in the tree's sap in the presence of moisture allows it to form a hard lacquer
, which is used to produce traditional Chinese
and Japanese
lacquerwares
.
with a boiling point of 200–210 °C. It is miscible in alcohol and ether, but nearly insoluble in water. Urushiol is a mixture of several closely related organic compound
s. Each consists of a catechol substituted with an alkyl chain that has 15 or 17 carbon atoms. The alkyl group may be saturated
or unsaturated; urushiol oil is a mixture of saturated and unsaturated molecules. The mixture varies with the vegetative species. Whereas western poison oak urushiol contains chiefly catechols with C17 side-chains, poison ivy
and poison sumac
yield mostly catechols with C15 side-chains. The allergic reaction is dependent on the degree of unsaturation of the alkyl chain. Less than half of the general population reacts with the saturated urushiol alone, but over 90% react with urushiol containing at least two degrees of unsaturation (double bonds). Moreover longer side chains tend to produce stronger sensitizers. This suggests that the allergic contact dermatitis is caused by Van der Waals' forces. Before Urushiol has been absorbed by the skin it can be removed with water. However, time is of great importance as 50% of urushiol is absorbed in 10min. Once Urushiol has penetrated into the skin, attempting to remove with water is inefficient. Once urushiol has been absorbed by the skin it is recognized by dendritic cells called langerhans cell
s that are part of the immune system, these cells then migrate to lymph nodes where they present the urushiol to T-lymphocytes and thus recruit them to the skin, once in the skin the T-lymphocytes cause pathology by producing cytokines and cytotoxic damage to the skin.
The urushiol liquid is an oleoresin
contained within the sap of poison ivy and related plants, and after injury to the plant or during late fall, the sap leaks to the surface of the plant, where the urushiol becomes a blackish lacquer
after contact with oxygen.
Allergen
An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....
found in plants of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Anacardiaceae
Anacardiaceae
Anacardiaceae are a family of flowering plants bearing fruits that are drupes and in some cases producing urushiol, an irritant. Anacardiaceae include numerous genera with several of economic importance. Notable plants in this family include cashew , mango, poison ivy, sumac, smoke tree, and marula...
, especially Toxicodendron
Toxicodendron
Toxicodendron a genus of flowering plants in the sumac family, Anacardiaceae. It contains woody trees, shrubs and vines, including poison ivy, poison oak, and the lacquer tree. All members of the genus produce the skin-irritating oil urushiol, which can cause a severe allergic reaction...
spp. (e.g., poison oak
Poison oak
Poison oak may refer to* Toxicodendron diversilobum, grows on West Coast of North America* Toxicodendron pubescens, grows in the Eastern United Statesdamnnnnn tissss is terribleee...
, poison ivy
Poison ivy
Toxicodendron radicans, better known as poison ivy , is a poisonous North American plant that is well known for its production of urushiol, a clear liquid compound found within the sap of the plant that causes an itching rash in most people who touch it...
, poison sumac
Poison Sumac
Poison sumac is a woody shrub or small tree growing to 7 m tall. All parts of the plant contain a resin called urushiol that causes skin and mucous membrane irritation to humans...
). It causes an allergic skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
rash on contact, known as urushiol-induced contact dermatitis
Urushiol-induced contact dermatitis
Urushiol-induced contact dermatitis is the medical name given to allergic rashes produced by the oil urushiol, which is contained in various plants, including the plants of the genus Toxicodendron , other plants in the family Anacardiaceae Urushiol-induced contact dermatitis (also called...
. The name comes from the Japanese
Japanese language
is a language spoken by over 130 million people in Japan and in Japanese emigrant communities. It is a member of the Japonic language family, which has a number of proposed relationships with other languages, none of which has gained wide acceptance among historical linguists .Japanese is an...
word Kiurushi which denotes a lacquer
Lacquer
In a general sense, lacquer is a somewhat imprecise term for a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required...
produced in East Asia
East Asia
East Asia or Eastern Asia is a subregion of Asia that can be defined in either geographical or cultural terms...
from the sap of Toxicodendron vernicifluum (the Lacquer Tree). The oxidation and polymerization of urushiol in the tree's sap in the presence of moisture allows it to form a hard lacquer
Lacquer
In a general sense, lacquer is a somewhat imprecise term for a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required...
, which is used to produce traditional Chinese
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and Japanese
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
lacquerwares
Lacquerware
Lacquerware are objects decoratively covered with lacquer. The lacquer is sometimes inlaid or carved. Lacquerware includes boxes, tableware, buttons and even coffins painted with lacquer in cultures mostly in the Eastern Hemisphere.-History:...
.
Characteristics
Urushiol is a yellow liquidLiquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
with a boiling point of 200–210 °C. It is miscible in alcohol and ether, but nearly insoluble in water. Urushiol is a mixture of several closely related organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
s. Each consists of a catechol substituted with an alkyl chain that has 15 or 17 carbon atoms. The alkyl group may be saturated
Saturation (chemistry)
In chemistry, saturation has six different meanings, all based on reaching a maximum capacity...
or unsaturated; urushiol oil is a mixture of saturated and unsaturated molecules. The mixture varies with the vegetative species. Whereas western poison oak urushiol contains chiefly catechols with C17 side-chains, poison ivy
Poison ivy
Toxicodendron radicans, better known as poison ivy , is a poisonous North American plant that is well known for its production of urushiol, a clear liquid compound found within the sap of the plant that causes an itching rash in most people who touch it...
and poison sumac
Poison Sumac
Poison sumac is a woody shrub or small tree growing to 7 m tall. All parts of the plant contain a resin called urushiol that causes skin and mucous membrane irritation to humans...
yield mostly catechols with C15 side-chains. The allergic reaction is dependent on the degree of unsaturation of the alkyl chain. Less than half of the general population reacts with the saturated urushiol alone, but over 90% react with urushiol containing at least two degrees of unsaturation (double bonds). Moreover longer side chains tend to produce stronger sensitizers. This suggests that the allergic contact dermatitis is caused by Van der Waals' forces. Before Urushiol has been absorbed by the skin it can be removed with water. However, time is of great importance as 50% of urushiol is absorbed in 10min. Once Urushiol has penetrated into the skin, attempting to remove with water is inefficient. Once urushiol has been absorbed by the skin it is recognized by dendritic cells called langerhans cell
Langerhans cell
Langerhans cells are dendritic cells of the skin and mucosa, and contain large granules called Birbeck granules. They are present in all layers of the epidermis, but are most prominant in the stratum spinosum. They also occur in the papillary dermis, particularly around blood vessels, as well as...
s that are part of the immune system, these cells then migrate to lymph nodes where they present the urushiol to T-lymphocytes and thus recruit them to the skin, once in the skin the T-lymphocytes cause pathology by producing cytokines and cytotoxic damage to the skin.
The urushiol liquid is an oleoresin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...
contained within the sap of poison ivy and related plants, and after injury to the plant or during late fall, the sap leaks to the surface of the plant, where the urushiol becomes a blackish lacquer
Lacquer
In a general sense, lacquer is a somewhat imprecise term for a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required...
after contact with oxygen.
See also
- Cashew nutshell liquidCashew nutshell liquidThe cashew nutshell liquid or cashew shell oil is a natural resin found in the honeycomb structure of the cashew nutshell. It consists of about 90% anacardic acids and 10% cardol...
(CNSL) - Urushiol-induced contact dermatitisUrushiol-induced contact dermatitisUrushiol-induced contact dermatitis is the medical name given to allergic rashes produced by the oil urushiol, which is contained in various plants, including the plants of the genus Toxicodendron , other plants in the family Anacardiaceae Urushiol-induced contact dermatitis (also called...
- Burow's solutionBurow's solutionBurow's solution is a pharmacological preparation made of aluminium acetate dissolved in water. It was invented in the mid-19th century by Karl August Burow, an ophthalmologist....
, for treating the toxin - Bentoquatam, a barrier creme
- HaptenHaptenA hapten is a small molecule that can elicit an immune response only when attached to a large carrier such as a protein; the carrier may be one that also does not elicit an immune response by itself...
- Ginkgo biloba
- Poison ivyPoison ivyToxicodendron radicans, better known as poison ivy , is a poisonous North American plant that is well known for its production of urushiol, a clear liquid compound found within the sap of the plant that causes an itching rash in most people who touch it...
- Western Poison-oakWestern Poison-oakToxicodendron diversilobum, western poison oak or Pacific poison-oak is in the Anacardiaceae family and is a plant best known for its ability to cause allergic rashes after contact...
- CashewCashewThe cashew is a tree in the family Anacardiaceae. Its English name derives from the Portuguese name for the fruit of the cashew tree, caju, which in turn derives from the indigenous Tupi name, acajú. It is now widely grown in tropical climates for its cashew nuts and cashew apples.-Etymology:The...
- MangoMangoThe mango is a fleshy stone fruit belonging to the genus Mangifera, consisting of numerous tropical fruiting trees in the flowering plant family Anacardiaceae. The mango is native to India from where it spread all over the world. It is also the most cultivated fruit of the tropical world. While...
- PistachioPistachioThe pistachio, Pistacia vera in the Anacardiaceae family, is a small tree originally from Persia , which now can also be found in regions of Syria, Lebanon, Turkey, Greece, Kyrgyzstan, Turkmenistan, India, Pakistan, Egypt, Sicily and possibly Afghanistan , as well as in the United States,...
- Anti-itch drug
- Anacardic acidAnacardic acidAnacardic acids are chemical compounds found in the shell of the cashew nut . As they are closely related to urushiol, they also cause an allergic skin rash on contact, known as urushiol-induced contact dermatitis. Anacardic acid is a yellow liquid. It is miscible partially in alcohol and ether,...
- Lithraea causticaLithraea causticaLithraea caustica is a species of flowering plants in the soapberry family Anacardiaceae. This plant occurs in central Chile; an example occurrence is in the area of La Campana National Park and Cerro La Campana...
External links
- Poison Oak at Wayne's Word
- The Poison Ivy Tutorial