Print this page

Poison Oak

What is poison oak and what are the varieties?

Western poison oak, a bushy shrub or climbing vine, can be found all along the Pacific Coast, from southern Canada down to the Baja California peninsula. Poison oak grows from sea level to as high as 5,000 feet. Characterized by alternate leaves with three or occasionally five veined, shiny leaflets, Western poison oak grows along the California coast. In fall, the leaves turn deep red.

Atlantic poison oak is native to the sandy soils of the eastern/southeastern United States and can be found as far west as Texas and Oklahoma. Atlantic poison oak is distinguished by three leaflets on each leaf, a hairy or fuzzy appearance and a resemblance to white oak leaves. In the fall the leaves turn yellow or orange.

Exposure to the oily sap of either variety contained throughout poison oak – roots, stem, leaves, flowers, and the fruit (berries) – can result in skin irritation ranging from mild to severe. Between 50% and 85% of the population is allergic to poison oak, causing a more severe reaction when exposed.

Primary contamination results from contact with bruised or broken plant parts that release toxicodendrol, an oily resin containing the toxic chemical urushiol. Because the lacquer-like resin does not dissolve in water, it is hard to wash off.

What are the causes of poison oak and who is likely to get it?

Fluid in the blisters does not contain the toxic poison oak chemical, urushiol. If the blisters break, the fluid will not result in spreading of the poison oak. Scratching other parts of the body with contaminated fingernails, however, may spread poison oak, and urushiol can remain under the nails for several days unless the nails are extensively cleaned. A person who has washed thoroughly and has changed into clean clothing will not spread poison oak. The only way to get poison oak is through direct contact with the toxic resin, for example by coming in contact with a contaminated person who has not washed properly or changed into clean clothes.

Other secondary exposures may result from handling garden, hunting or sports equipment, or camping gear exposed to poison oak. Thick fur protects most pets that run through poison oak patches from developing symptoms. However, people who touch contaminated pets can come directly in contact with the resin and may develop poison oak. What are the symptoms?

Severity of poison oak skin reaction depends on the degree of patient sensitivity, the amount of exposure, and on which body parts are exposed. Sensitive body parts, including the eyes, lips, and genitals exposed to poison oak sap will experience a more severe reaction.

Skin irritation characterized by redness, blistering, swelling and severe itching generally develops 24-48 hours after the exposure. Some victims experience symptoms after as little as 30 minutes. Others may not have symptoms until 14 days following exposure. In typical cases, the reaction is most severe five days after the exposure. Mild cases of poison oak last from seven to 10 days. Severe cases may last up to three weeks or longer. People with pale skin are more susceptible than dark-skinned people and younger people are more susceptible than the elderly.

Burning poison oak will produce a dangerous smoke that can cause severe symptoms to the eyes, nose, throat and lungs.

How is it diagnosed?

The main symptom of poison oak, poison ivy, or sumac is an extremely itchy, red rash that appears within 24 to 72 hours of exposure to the oil. The rash often appears streaked, and may develop into oozing blisters. In general, the skin rash may be uncomfortable. It is not serious, though, and usually resolves on its own in one to two weeks. However, you should contact a doctor immediately if you are highly sensitive or have the following symptoms:

  • swelling of the face or throat
  • rash on the genitals
  • swelling or rash that covers more than one third of your body
  • rapidly spreading rash
  • signs of a bacterial infection, such as pain, increased redness, or pus.

Diagnosis of poison ivy, oak, or sumac is based on the presence of a characteristic itchy rash, and possible exposure to plants containing urushiol oil.

What is the conventional treatment of poison oak?

Treatment consists mostly of protecting the damaged skin, preventing infection and relieving the itching. Over-the-counter medications may be used as poison oak treatments and as a poison ivy remedy. Store-brand or generic versions of these medications also work and are usually available. If the case of poison oak is severe, you should see a physician for more extensive poison oak treatment with stronger steroid medications.

Avoid the use of older Caladryl that contains the ingredient "diphenhydramine," unless directed by your physician. Applying diphenhydramine to open sores and taking diphenhydramine by mouth can cause a toxic build-up of the drug.

What therapies does Dr. Weil recommend for poison oak?

The best poison oak/poison ivy treatment is to run hot water on the affected areas, as hot as you can stand. This will seem counterintuitive, since heat increases the itching and cold soothes it. Under hot water the itching will briefly become very intense and then will stop for several hours, as if the nerves responsible for conveying the sensation to the brain become overloaded and quit. As soon as the itching starts again, go back to the hot water. If you do this conscientiously the whole reaction will complete itself quickly and your skin will return to normal much faster than it would otherwise.

  • If you wish, use calamine lotion as a topical treatment for poison oak.
  • Aloe vera gel can help heal skin irritated by scratching.
  • Do not take oral prednisone for poison oak or ivy unless the cause is so severe that you become systematically ill (fever, difficulty in urinating, etc.) Do not use topical steroids unless specifically instructed to do so by a physician.
  • Change clothing as soon as possible after exposure and handle contaminated clothing carefully to avoid spreading the poison oak. Launder clothes several times before re-wearing.
  • Never burn poison oak.
  • Do NOT wash the body with any concentration of liquid bleach after a poison oak exposure. Bleach is not helpful and the vapors can be irritating to the eyes, nose, throat and lungs. Bleach will irritate inflamed skin even more, causing redness and pain to sensitive body parts.

How poison oak can be prevented:

  • Learn to recognize poison oak and teach kids to recognize it. "Leaves of three, let it be."
  • Wear protective clothing when outdoors.
  • Keep animals from running through poison oak areas.