Urushiol-induced contact dermatitis
Encyclopedia
Urushiol-induced contact dermatitis (also called Toxicodendron dermatitis and Rhus dermatitis) is the medical name given to allergic
rash
es produced by the oil urushiol
, which is contained in various plants, including the plants of the genus Toxicodendron
(including poison ivy
, poison oak, and poison sumac
), other plants in the family Anacardiaceae
(mango
, Rengas tree, Burmese lacquer tree, India marking nut tree, and the shell of the cashew
nut), and 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 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, but also problematic.
prescription is necessary to stop skin damage, especially if the eyes are involved. The rash persists typically one to two weeks and in some cases up to five weeks. At least 25% of people have very strong responses resulting in severe symptoms. Since the skin reaction is an allergic one, people may develop progressively stronger reactions after repeated exposures.
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 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 can 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. Firefighters often get rashes and eye inflammation from smoke-related contact. A high-temperature, fully inflamed bonfire may 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.
are indirect, mediated by an induced immune response. Urushiol
acts as a hapten
, chemically reacting with, binding to, and changing 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, 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.
tous contact dermatitis
characterized by redness, swelling, papule
s, vesicles, blister
s, and streaking. People vary greatly in their sensitivity to urushiol. In approximately 15% to 30% 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.
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, 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 (Epstein et al., 1974).
The rash takes one to two weeks to run its course and 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 staphylococcal
and streptococcal
species; these may require the use of antibiotics.
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 also contain abrasive
s.
Showers or compresses using very hot water (but not scalding) can offer relief of itching for up to several hours, with the caveats that this "also taxes the skin's integrity, opening pores and generally making it more vulnerable", and is only for secondary treatment (not while cleaning urushiol from the skin, which should be done with cold water). Those 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 by applying moderate cold to any infected skin with biting pain.
Antihistamine
s and hydrocortisone creams or antihistamines by mouth in severe cases can be used to alleviate the symptoms of a developed rash. Nonprescription oral diphenhydramine
(US tradename Benadryl
) is the most commonly suggested antihistamine. Topical formulations containing diphenhydramine are available, but may further irritate the affected skin areas. 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.
In cases of extreme symptoms, steroids such as prednisone
are sometimes administered to attenuate the immune response.
Prednisone is the most commonly prescribed systemic treatment, but can cause serious adrenal suppression changes, so it must be taken carefully, tapering off slowly. If bacterial secondary infection of affected areas occurs, antibiotics may also be necessary.
Many home remedies
and even commercial products (e.g., Zanfel and Tecnu
) claim to prevent urushiol rashes after the exposure. A study of such a product, Tecnu, and ordinary soap, Goop and Dial soap, found 70%, 62%, and 56% protection relative to the possible maximum response, at costs per ounce of $1.25, $0.07, and $0.07. The study compared four 2.5 cm exposed squares on the inner aspect of the forearm, three of which were treated and one untreated. Some clarifications:
Allergy
An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...
rash
Rash
A rash is a change of the skin which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell and may be painful. The causes, and...
es produced by the oil urushiol
Urushiol
Urushiol is an oily organic allergen found in plants of the family Anacardiaceae, especially Toxicodendron spp. . It causes an allergic skin rash on contact, known as urushiol-induced contact dermatitis...
, which is contained in various plants, including the plants of the genus 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...
(including 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 oak, 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...
), other plants in the family 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...
(mango
Mango
The 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...
, Rengas tree, Burmese lacquer tree, India marking nut tree, and the shell of the cashew
Cashew
The 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...
nut), and 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
American Academy of Dermatology
The American Academy of Dermatology is the largest organization of dermatologists in the world. It was founded in 1938 and represents 17,000 dermatologists in the United States, Canada, and around the world. The Academy grants Fellowships and Associate Memberships, as well as Fellowships for...
estimates there are up to 50 million cases of urushiol-induced dermatitis annually in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
alone, accounting for 10% of all lost-time injuries in the United States Forest Service
United States Forest Service
The United States Forest Service is an agency of the United States Department of Agriculture that administers the nation's 155 national forests and 20 national grasslands, which encompass...
. 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...
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
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...
is less common, but also 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 with which it comes in contact, such as towels, blankets and 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; for those with severe reactions, it will worsen during the next few days. For severe reactions, a prednisonePrednisone
Prednisone is a synthetic corticosteroid drug that is particularly effective as an immunosuppressant drug. It is used to treat certain inflammatory diseases and some types of cancer, but has significant adverse effects...
prescription is necessary to stop skin damage, especially if the eyes are involved. The rash persists typically one to two weeks and in some cases up to five weeks. At least 25% of people have very strong responses resulting in severe symptoms. Since the skin reaction is an allergic one, people may develop progressively stronger reactions after repeated exposures.
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 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 can 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. Firefighters often get rashes and eye inflammation from smoke-related contact. A high-temperature, fully inflamed bonfire may 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.
Mechanism
The toxic effects of urushiolUrushiol
Urushiol is an oily organic allergen found in plants of the family Anacardiaceae, especially Toxicodendron spp. . It causes an allergic skin rash on contact, known as urushiol-induced contact dermatitis...
are indirect, mediated by an induced immune response. Urushiol
Urushiol
Urushiol is an oily organic allergen found in plants of the family Anacardiaceae, especially Toxicodendron spp. . It causes an allergic skin rash on contact, known as urushiol-induced contact dermatitis...
acts as a hapten
Hapten
A 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...
, chemically reacting with, binding to, and changing the shape of integral membrane protein
Integral membrane protein
An integral membrane protein is a protein molecule that is permanently attached to the biological membrane. Proteins that cross the membrane are surrounded by "annular" lipids, which are defined as lipids that are in direct contact with a 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, 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 eczemaEczema
Eczema is a form of dermatitis, or inflammation of the epidermis . In England, an estimated 5.7 million or about one in every nine people have been diagnosed with the disease by a clinician at some point in their lives.The term eczema is broadly applied to a range of persistent skin conditions...
tous contact dermatitis
Contact dermatitis
Contact dermatitis is a term for a skin reaction resulting from exposure to allergens or irritants . Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight....
characterized by redness, swelling, papule
Papule
A papule is a circumscribed, solid elevation of skin with no visible fluid, varying in size from a pinhead to 1 cm.With regard to the quote "...varying in size from a pinhead to 1cm," depending on which text is referenced, some authors state the cutoff between a papule and a plaque as 0.5cm,...
s, vesicles, blister
Blister
A blister is a small pocket of fluid within the upper layers of the skin, typically caused by forceful rubbing , burning, freezing, chemical exposure or infection. Most blisters are filled with a clear fluid called serum or plasma...
s, and streaking. People vary greatly in their sensitivity to urushiol. In approximately 15% to 30% 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.
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, 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 (Epstein et al., 1974).
The rash takes one to two weeks to run its course and 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
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
, commonly by staphylococcal
Staphylococcus
Staphylococcus is a genus of Gram-positive bacteria. Under the microscope they appear round , and form in grape-like clusters....
and streptococcal
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
species; these may require the use of antibiotics.
Treatments
Potential treatments are in two phases: stopping the urushiol contact causing a reaction with the skin (this must be done within minutes), and later in reducing the pain or pruritus (itching) of any blistering that has formed.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
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
s, such as the nonionic detergent
Detergent
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...
Triton X-100 to solubilize urushiol; some preparations also contain abrasive
Abrasive
An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away...
s.
Showers or compresses using very hot water (but not scalding) can offer relief of itching for up to several hours, with the caveats that this "also taxes the skin's integrity, opening pores and generally making it more vulnerable", and is only for secondary treatment (not while cleaning urushiol from the skin, which should be done with cold water). Those 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 by applying moderate cold to any infected skin with biting pain.
Antihistamine
Antihistamine
An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...
s and hydrocortisone creams or antihistamines by mouth in severe cases can be used to alleviate the symptoms of a developed rash. Nonprescription oral diphenhydramine
Diphenhydramine
Diphenhydramine hydrochloride is a first-generation antihistamine possessing anticholinergic, antitussive, antiemetic, and sedative properties which is mainly used to treat allergies. Like most other first-generation antihistamines, the drug also has a powerful hypnotic effect, and for this reason...
(US tradename Benadryl
Benadryl
Benadryl is a brand name allergy medicine marketed over-the-counter by Johnson & Johnson subsidiary McNeil Consumer Healthcare. Prior to 2007, Benadryl was marketed by Pfizer Consumer Healthcare...
) is the most commonly suggested antihistamine. Topical formulations containing diphenhydramine are available, but may further irritate the affected skin areas. 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.
In cases of extreme symptoms, steroids such as prednisone
Prednisone
Prednisone is a synthetic corticosteroid drug that is particularly effective as an immunosuppressant drug. It is used to treat certain inflammatory diseases and some types of cancer, but has significant adverse effects...
are sometimes administered to attenuate the immune response.
Prednisone is the most commonly prescribed systemic treatment, but can cause serious adrenal suppression changes, so it must be taken carefully, tapering off slowly. If bacterial secondary infection of affected areas occurs, antibiotics may also be necessary.
Many home remedies
Home remedy
A home remedy is a treatment to cure a disease or ailment that employs certain spices, vegetables, or other common items. Home remedies may or may not have medicinal properties that treat or cure the disease or ailment in question, as they are typically passed along by laypersons...
and even commercial products (e.g., Zanfel and Tecnu
Tecnu
Tecnu is an over-the-counter skin cleanser manufactured by Tec Labs, a pharmaceutical company based in Albany, Oregon. It is intended for use by humans and furry pets after topical exposure to urushiol, the active ingredient in poison oak, poison ivy, and poison sumac...
) claim to prevent urushiol rashes after the exposure. A study of such a product, Tecnu, and ordinary soap, Goop and Dial soap, found 70%, 62%, and 56% protection relative to the possible maximum response, at costs per ounce of $1.25, $0.07, and $0.07. The study compared four 2.5 cm exposed squares on the inner aspect of the forearm, three of which were treated and one untreated. Some clarifications:
- 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. One home remedy includes laundering clothes with Fels-NapthaFels-NapthaFels-Naptha is a brand of bar laundry soap used for pre-treating stains on clothing and as a home remedy for exposure to poison ivy and other skin irritants. Fels-Naptha is manufactured by and is a trademark of the Dial Corporation.-Use:...
- The fluid from the resulting blisters does not spread poison ivy to others.
- Blisters should be left unbroken during healing.
- 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, cold water, cooling lotions, or cold air do not help cure poison ivy rashes, but cooling can reduce inflammation and soothe the itch.
- 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....
, calamine lotion and Jewelweed are ineffective or of questionable effectiveness against itching.
See also
- 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...
- Contact dermatitisContact dermatitisContact dermatitis is a term for a skin reaction resulting from exposure to allergens or irritants . Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight....
- Anti-itch drug
- ToxinToxinA toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...
- List of cutaneous conditions