Urushiol

Urushiol

Chemical structure of urushiol

Urushiol is an oily organic allergen found in plants of the family Anacardiaceae, especially in the genera Toxicodendron (e.g., poison ivy, poison oak, and poison sumac). It is the substance responsible for the itchy and often painful rash known as urushiol-induced contact dermatitis.

Chemical Composition

Urushiol is a mixture of several closely related organic compounds. These compounds are derivatives of catechol with a hydrocarbon chain that varies in length and degree of unsaturation. The most common form of urushiol in poison ivy is 3-pentadecylcatechol.

Mechanism of Action

Mechanism of urushiol-induced contact dermatitis

Urushiol binds to the skin upon contact and modifies skin proteins, making them appear foreign to the immune system. This triggers an immune response, primarily involving T cells, which leads to the symptoms of contact dermatitis. The reaction typically occurs 12 to 48 hours after exposure and can last for several weeks.

Sources

Urushiol is found in the sap of plants such as poison ivy, poison oak, and poison sumac. It is also present in the lacquer tree (Toxicodendron vernicifluum), which is used to produce traditional Japanese lacquerware.

Symptoms of Exposure

Exposure to urushiol can cause a range of symptoms, including redness, swelling, blistering, and severe itching. The severity of the reaction can vary depending on the individual's sensitivity and the amount of urushiol exposure.

Prevention and Treatment

Avoiding contact with urushiol-producing plants is the best prevention. If contact occurs, washing the skin with soap and water within 10 to 15 minutes can help remove the oil. Over-the-counter treatments such as calamine lotion and hydrocortisone cream can alleviate symptoms. In severe cases, prescription medications may be necessary.

Related Media

Video explaining how poison ivy works

Related Pages

• Poison ivy
• Poison oak
• Poison sumac
• Contact dermatitis

References

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