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Poison Oak Rash: Causes, Characteristics & Treatment

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What is Poison Oak Rash?

Poison oak rash is caused by urushiol, an oily sap found in the leaves, stems and roots of the poison oak plant.  After an encounter with the plant, a rash may develop within 12 to 72 hours (x). Poison oak rash is a form of contact dermatitis. It can cause redness, itching, swelling and blisters or hives on the skin. Most cases of poison oak rash resolve within one to two weeks, but in extreme cases, the rash may persist for longer. The medical term for poison oak rash is Toxicodendron dermatitis because the plant is from the Toxicodendron family (x).

People of all skin types can develop poison oak rash. The rash may be more severe in older patients. Those who work in forestry, firefighting and agriculture may have a greater risk of poison oak rash from repeated exposure to the plant (x).

Characteristics of Poison Oak Rash

Poison oak rash starts as a mild skin irritation, which gradually develops into a red, itchy rash. Bumps may form on the skin and the rash may start to blister. In some cases, poison oak rash may develop into a bacterial infection (x).

Poison oak can also cause a rash even if the patient does not come in direct contact with it. For example, touching any object that has the urushiol can cause a rash. If the plant burns, urushiol can enter the lungs and cause respiratory complications.

When to Seek Medical Attention

Anyone with poison oak rash should seek medical help if they experience any of the following symptoms (x):

  • Itching that will not subside 
  • A rash that does not improve
  • Fever
  • Rash that spreads to the face or genitals
  • Tenderness, soft yellow scabs or pus on the rash
  • Difficulty breathing or swallowing
  • Swelling, especially in the eyelids
Characteristics of Poison Oak Rash

Causes of Poison Oak Rash

Poison oak, or Toxicodendron diversilobum, grows all over the continental United States, especially west of the Rocky Mountains and in the eastern U.S. The plant is also called Pacific poison oak or Western poison oak. It is either a shrub or a woody vine that grows in North American forests and grasslands. The plant has thorny or hairy stems and bears greenish-white berries in the summer and fall (x). The poison oak plant rarely grows in high elevations (above 4,000 ft.), desert areas (except along streams, riverbanks and ponds) or in Hawaii, Alaska and the Midwest (x).

What is Urushiol?

Urushiol is an oily mixture of organic compounds. It is present in the roots, stems and leaves of the poison oak plant. About 50 to 70 percent of the population is sensitive to this allergen (x). Its compounds are colorless and odorless, but the effects are toxic and long-lasting. Once it contaminates clothing or other objects or surfaces, urushiol remains active and it can contaminate the next person to have contact with it. Urushiol can remain in the plant throughout the winter and it may also be active in the roots of a dead plant. If a plant containing urushiol burns, the smoke can also cause an allergic reaction.

After a person touches urushiol, the allergen penetrates the skin quickly, which triggers an immune system response. A reaction to urushiol happens in three phases. First, the skin is red and itchy. Then a patchy or streaked rash develops, following the pattern where the skin made contact. Then the rash turns into red bumps or large blisters (x).

Why Does the Body React to Urushiol?

Researchers have concluded that urushiol causes a reaction because of a protein molecule in the skin called CD1a. The molecule plays a role in inflammatory skin disorders (x). When urushiol interacts with the body, the CD1a protein activates the immune system. The immune system’s T-cells respond by producing two more proteins, causing the aggravating itch and inflammation (x, x).

How to Identify Poison Oak Leaves

  • Groups of three leaflets
  • Most often a shrub, but it may grow as a vine
  • Yellow-white berries (x)

Other Plants that Contain Urushiol

Poison oak is not the only plant that contains urushiol. Other species in the same plant family Anacardiaceae also contain it and cause similar reactions. Even unrelated plants may contain similar toxins.

Poison Ivy

Poison ivy is infamous for its itchy and bothersome rash. It grows throughout North America and in Asia as a vine or small shrub. Its glossy leaves turn reddish in the spring and green in summer. It may also display yellowish-white berries and colored leaves again in the fall. Birds and other animals may rely on its seeds, berries and leaves for food and cover (x).

Poison Sumac

Poison sumac looks like a woody shrub or a small tree and it grows in wet, swampy areas. This plant has drooping green berries, but harmless sumacs have red, upright berries. Poison sumac grows in the northeast, the Midwest and southeastern regions of the United States. Like other plants that contain urushiol, poison sumac causes redness and an irritating rash with contact (x).

Lacquer Tree

The lacquer tree contains urushiol and varnish from the lacquer tree can also cause dermatitis. It grows in Asia and is one of the most common causes of allergic reactions (x).

Mango

Mangoes contain urushiol in the outer skin. If an individual bites into an unpeeled mango and they are sensitive, they may experience a slight allergic reaction on the face and around the mouth (x).

Cashews and Pistachios

The cashew nut tree contains an element that is chemically similar to urushiol. Roasting them destroys the toxin, but harvesters who touch the raw cashews may develop a rash from exposure to the oil (x). Pistachios also contain urushiol, but they do not seem to cause a rash (x).

Ginkgo Biloba

The Ginkgo biloba tree, found on the Asian continent in temperate countries, also contains a urushiol-like sap that can also cause an allergic skin reaction (x).

Preventing Poison Oak Rash

Anyone that enjoys the outdoors can take steps to prevent exposure to poison oak. Learn to identify poison oak in order to avoid contact with it. Remove these plants from yards where they may grow. Pull the plant out by the root and use white vinegar to kill any lingering seedlings. Wear heavy gloves to protect the skin.

Do not set fire to poison oak plants because the oil can become airborne and cause extreme respiratory distress, especially in those with asthma or other respiratory conditions. Do not let pets run in wooded areas where they make contact with poisonous plants and carry the urushiol on their fur. Keep skin covered with long sleeves, long pants, shoes and socks to walk or work outside.

Treating Poison Oak Rash

Poison oak rash usually does not require any medical treatment. The rash usually goes away in a few weeks. But cool showers and medicated lotions can help relieve itching and discomfort. If the reaction involves the mucus membranes in the mouth, nose or eyes, the patient may need a prescription for corticosteroid medication. Don’t scratch the rash, because it can break the blisters or cause an infection (x).

After contact with the plant, remove and wash all clothing. Wash exposed skin with cool water and soap. Washing the area within 10 to 15 minutes after exposure may prevent the rash from developing. Make sure to also clean under the fingernails as well. Using rubber gloves, wash all tools and equipment that may have made contact with the plant. Bathe pets exposed to it as well (x).

Rubbing Alcohol

Rubbing alcohol can eliminate urushiol on any surface where it may linger. Touching a surface with urushiol on it can cause a reaction (x).

Cold Water

Soaking the skin in cold water may help relieve itching and redness. A cool compress may also help. Run a clean washcloth under cold water and apply it to the skin (x).

Astringents

Astringents may calm the rash and help it heal, such as witch hazel, apple cider vinegar and cold black tea. Soak a cloth in one of these liquids and apply it like a cold compress to reduce inflammation (x, x, x).

Topical Lotions & Creams

Pure aloe vera gel is an effective soothing balm for many different skin conditions (x). Over-the-counter lotions can also help relieve symptoms. Calamine lotion and hydrocortisone cream are common treatments to combat itching. If the rash is oozing, products that contain zinc acetate, zinc carbonate or zinc oxide can help (x).

Soothing Baths

Research suggests that oatmeal has anti-inflammatory benefits and may soothe the skin when in a bath. First, finely grind one cup of oatmeal and stir it into a lukewarm bath. Soak for 15-30 minutes. A cup of baking soda in a warm bath can also help relieve rashes (x).

Bentonite Clay

Some patients report relief from poison ivy rash after applying a paste of water and bentonite clay to the affected area. According to research, quaternium-18 bentonite may effectively reduce and prevent symptoms from contact dermatitis (x).

Medication

If a patient has a severe reaction, a doctor may prescribe medication to heal the reaction. Prescription corticosteroid drugs may help ease inflammation and itching. It may be a cream, gel, lotion, tablet or injection (x).

Supplements for Skin Health

Supplements may be helpful in cases of contact dermatitis, including poison oak rash. They can help the body fight infections and also help the skin heal itself from wounds or damage. However, they are not an adequate medical treatment. Consult a doctor before starting a supplement regimen and always follow a physician’s instructions.

Echinacea

Echinacea is a traditional herbal remedy to address several different conditions. It is especially useful as an anti-inflammatory that fights infection and inflammation and supports the immune system. The recommended serving size for echinacea extract powder is 450 mg (about ¼ tsp) once or twice a day, or following a physician’s instructions.

Vitamin C

Vitamin C is a good supplement to take to help the body fight anything, such as the common cold and flu or an infection. It is an antioxidant and a famous and effective immune booster. Vitamin C is also a key factor in healthy skin and collagen production. As a dietary supplement, take 1,000 mg of Vitamin C/ascorbic acid daily, after consulting a physician.

Nettle Leaf

Nettle leaf is a powerful antioxidant rich in nutrients. It can help promote healthy skin and ease inflammation in the skin, such as a poison oak rash (x). As a dietary supplement, take 750 mg (¼ tsp) of nettle extract powder once or twice daily, unless a physician suggests a different dosage.

Quercetin

Quercetin is a powerful element from plants, including blueberries and kale. It has benefits on longevity, cardiac health and the immune system. Research also shows its potential anti-inflammatory and anti-viral qualities (x). The recommended dosage for quercetin dihydrate powder is between 250 mg (¼ tsp) and 500 mg (½ tsp) once or twice a day, with a doctor’s approval.

Zinc

Zinc combined with the amino acid glycine absorbs quickly into the skin. This powerful combo boosts collagen production and elasticin. Zinc is a common treatment for inflammatory skin conditions because of its soothing and healing properties (x). As a dietary supplement, take 225 to 450 mg of zinc gluconate powder daily, or following a physician’s instructions.

The Bottom Line

Poison oak rash is caused by the oily sap urushiol, courtesy of the poison oak plant. When people learn to identify its glossy, oak-shaped, grouped clusters, they can avoid this irritating shrub. But poison oak often catches people and pets unaware as they tramp through the woods and causes an itchy, red, inflamed rash on the skin. It can even affect patients from indirect contact or breathing in the fumes from a burning poison oak plant.

Fortunately, washing with soap and water may help prevent the rash before it takes hold. And if the patient doesn’t act quickly enough, there are a number of ways to relieve the nasty symptoms naturally, as well as supplements to support the body as the rash runs its course. Usually the rash goes away on its own after a few weeks. But if an allergic or extreme reaction occurs, seek medical attention. Always consult a doctor before starting a supplement regimen for skin health. They are not a medical treatment. Instead, they aim to promote general health.

About the author

Lisa Luciano


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