by Joshua E. Lane, M.D.

My son is prone to a rash from poison ivy, and sometimes we can’t figure out how he could possibly have been exposed. Other than keeping his skin covered when outside, is it preventable? What are your recommendations for treating poison ivy?

Poison ivy (rhus dermatitis) is a characteristic cutaneous eruption—in lay terms, a rash—that may occur following exposure to the active agent, urushiol. Most individuals are sensitive to this toxin, which is found in poison ivy, oak and sumac. The classic appearance of the reaction is a linear streak of fluid-filled vesicles, which resemble tiny blisters.

The urushiol toxin often sticks to other objects such as pets, gardening tools, toys, etc. and can potentially cause eruptions, even if the plant itself is never touched. Furthermore, this residual toxin may remain potent for weeks if the items are not rinsed. Thus, your son may have been exposed even if he was never near the plant.

If you or your child is exposed to the plant or its toxin, wash with soap and water within five minutes to minimize the reaction. Also be sure to cleanse items that may be harboring the urushiol, such as outerwear, your pet’s fur and gardening tools, etc. to prevent indirect exposure.

Many people erroneously believe that scratching the lesions will cause the eruption to spread. People also think that poison ivy enters the bloodstream because it continues to erupt days after the exposure—neither is true. The reaction elicited by urushiol is a cell-mediated delayed hypersensitivity reaction, which means the itchy, fluid-filled vesicles may continue to erupt hours to days later. But eruptions will occur only in areas that were exposed to the urushiol, either directly from the plant or indirectly from another agent harboring the toxin. This is why, in hopes of reducing your exposure, it is important to quickly rinse the areas and objects that may have come in contact with the plant.

If an eruption does occur, a few simple recommended treatments include the following:
• Apply over-the-counter hydrocortisone cream.
• Colloidal oatmeal bathes may soothe inflammation.
• Avoid topical Neosporin and/or Benadryl cream. These are irritating and one of the most common causes of contact dermatitis.

Your dermatologist can prescribe topical and possibly oral corticosteroids for treatment. This may be necessary for severe cases in which over-the-counter topical therapy does not work.

Dr. Lane currently practices at Lane Dermatology & Dermatologic Surgery in Columbus. He is also a clinical assistant professor at the Emory University School of Medicine and at Mercer University School of Medicine, and is a clinical instructor at The Medical College of Georgia.

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