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Leaves of Three

Author: Steven Levenberg, D.O.
November, 2015 Issue

It’s important to recognize poison oak in all its seasonal phases to avoid contact.


We live in one of the most beautiful places on earth, surrounded by spectacular vistas softened by the verdant landscape that covers hills and valleys. But sometimes that verdant landscape just causes trouble. I’m not talking about the trouble we have as gardeners battling back the relentless progress of weeds. This month, I want to focus on one of the most common maladies we see in a family medicine office: poison oak.

Poison oak is the Western representative of a group of plants that also includes poison ivy and poison sumac. Poison oak is present all along the West Coast, from sea level to an elevation of 5,000 feet. All these plants share the characteristic of producing an oily sap, called urushiol, that can produce a severe allergic reaction in contact with human skin. If you recognize it—and you should—there’s almost nowhere in Sonoma County that you won’t find poison oak. Hot, cold, wet, dry: No matter what, this plant thrives.


Studies indicate that anywhere from 50 to 75 percent of people are sensitive to urushiol. One study indicated that 50 percent of workers’ compensation claims filed in California were for urushiol dermatitis, so this can have a big impact on your business if you have employees who work outdoors.


Prevention is the most powerful strategy. With poison oak, the adage is “leaves of three, leave them be.” When it’s in full leaf during spring, summer and early fall, the poison oak plant has groups of three beautiful shiny, deep green and red leaves. Once you know it, it’s hard to miss. In late fall and winter, the plant is more dormant and woody with few leaves, but the urushiol is still abundant in the wood and leaf debris and contact with any part of the plant can cause the rash. Absolutely avoiding contact is the first step.


The sticky and tenacious nature of the urushiol sap is what results in some of the biggest problems we see with poison oak. It’s not at all unusual for me to see patients in the office with a classic poison oak rash who have no idea how they were exposed. The urushiol can stick to clothing, bags, boots or shoes, tools and other objects, and it’s frequently brought into a household by pets. It can persist on surfaces and objects almost indefinitely. Bodies of water can develop a slick of urushiol sap if plants are in contact with the water. Serious systemic reactions sometimes result from contact with smoke that aerosolizes the sap when the plant is burned.


In situations where contact is possible (or likely), multiple measures can help prevent developing the rash. Thick clothing covering all bare skin is the first line of defense. Barrier creams (Ivy Block, Stokogard) can also be applied to prevent contact with the skin. Any areas of skin that might have been exposed should be washed as soon as possible in warm, soapy water; specialized soaps like Tecnu or Zanfel may be more effective at removing urushiol. It’s also important to wash systematically to avoid simply dispersing the urushiol without actually removing it. Don’t forget to carefully wash clothing and other objects (including furniture and car interiors) that may harbor urushiol and cause exposure days, weeks or even months later.


The rash may start anytime, from hours to days after exposure. It’s intensely itchy, raised and usually blistered. The fluid from the blisters will not spread the rash, but may spread residual urushiol oil that remains on the skin. Whether the rash remains confined or spreads widely depends on the extent of exposure, the amount of oil left on the skin after washing and a person’s particular sensitivity.


Treatment of the rash depends on the severity of the reaction and the extent of the rash. Keeping the affected areas clean is important to prevent infection. Topical products like calamine lotion can help relieve the itching. So can Benadryl cream, but copious application to open skin can result in absorption of unsafe amounts of Benadryl. Oral antihistamines can also help with itching. If limited areas are involved, sometimes treatment with topical steroid creams can be used.


Some people who are extremely affected with severe itching, widespread rash or extensive involvement of their face, eyes or genitals do require more aggressive treatment with oral cortisone (prednisone) for anywhere from a few days to weeks. In some cases, the open areas of the rash can become infected, requiring treatment with antibiotics.


Remember “leaves of three, leave them be.” Avoid trouble in paradise for you and your employees.


Dr. Steven Levenberg, a member of Sutter Medical Group of the Redwoods, is board certified in the specialty of family medicine. He’s been in practice for 30 years, in Cotati and Rohnert Park since 1989, and is a native of Santa Rosa.


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