Rhus dermatitis

Rhus dermatitis

Description, Causes and Risk Factors:

Urushiol-induced contact dermatitis, toxicodendron dermatitis.

Rhus dermatitis is also called Urushiol-induced contact dermatitis (Toxicodendron dermatitis) is the medical name given to allergic rashes produced by oil urushiol, which is contained in various plants, including the plants of the genus Toxicodendron (including poison ivy, 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.

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.

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.

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.


General Symptoms may include:


  • Burning skin.

  • Itching.

  • Redness of the skin.

  • Swelling.

At first, the skin that has touched the plant or the urushiol becomes red, and then bumps and blisters appear. This is usually accompanied by itching and sometimes by swelling. After reaching their peak in several days, the blisters break and the oozing sores begin to crust over and disappear. The rash rarely occurs on the scalp, palms of the hands, or soles of the feet because the outer skin there is very tough, and it is difficult for the plant oil to penetrate. Scratching the rash may introduce bacteria into the open sores, causing a secondary bacterial infection. Severe infections may produce symptoms such as abscesses, enlarged glands, and fever.


The first step in diagnosing the cause of rhus dermatitis is to obtain a medical history. The doctor will ask questions about the patient's activities and environment before the rash appeared, chemicals used in work or hobby activities, medications or cosmetics applied, and other exposures that might serve as clues to the cause.

The history as well as the typical appearance and location of the rash are often sufficient to implicate one of the Toxicodendron plants as the cause of the dermatitis. When a doctor needs to confirm suspicions of an allergy, a patch test can be performed. Because the material used in the patch test itself may sensitize patients to urushiol, the test should be used only when necessary for diagnosis — not as a routine procedure. In any case, the test should not be done until all active sores have healed because testing can aggravate the condition further.


Potential treatments are in two phases: Stopping the urushiol contact causing a reaction with the skin (this must be done within minutes), or later in reducing the pain 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 surfactants such as the nonionic detergent Triton X-100 to solubilize urushiol. Some preparations additionally contain abrasives.

Try over-the-counter anti-itch products for minor itching or swelling or check with your pharmacist.

A person should see a physician if the rash is severe, is on the face or genitals, or covers more than 20 percent of the body. The physician may prescribe medicines to reduce itching and inflammation. These may include antihistamines to be taken by mouth and corticosteroid lotions and creams to be applied to the skin. The doctor may prescribe oral corticosteroids in severe cases but also in some moderate ones.


    Learn to recognize poison ivy and avoid exposure.

  • Always wear vinyl gloves when removing plants (urushiol can penetrate rubber).

  • Wear long pants, long sleeves, socks, closed shoes, hat when walking in areas with poison ivy.

  • Do not burn poison ivy.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

Reference and Source are from:

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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