An 8-year-old girl presents with a red swollen eye and an erythematous rash on her face, arms and legs during the summer months.An intensely itchy red, linear mark that rapidly progressed to bumps and blisters first appeared on the girl’s forearm, and spread to her face and legs within days.The girl’s parents did not report anything clinically significant in the medical history or any out of the ordinary events, but noted that the girl spends a lot of time playing outdoors. What’s your diagnosis?Submit your answer, and then read the full explanation below. If you like this activity or have a suggestion, tell us about it in the comment box at the bottom of the page.
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Poison ivy contact dermatitis is an allergic reaction to an oily resin called urushiol produced by plants that belong to the Anacardaceae plant family, and affects as much as 70% of the population in North America. Reports of allergic contact dermatitis exacerbated by poison ivy, also known as Toxicodendron radians, tend to increase in the spring and summer but can occur year round.
After first exposure, allergic individuals are sensitized within seven to 12 days, but in subsequent exposures a rash may appear within 12 hours. Reactions can occur after direct exposure, urushiol that remains on the skin and is then transferred to other areas, urushiol on objects and from enhaling smoke from the burning allergen.
Poison ivy dermatitis is not contagious, as blister fluid does not contain urushiol, but the rash can be spread through contact with an individual that has urushiol on their skin or clothing. Secondary bacterial infection can occur from scratching and is signified when blisters ooze pus.
Most patients with poison ivy contact dermatitis do not need treatment, unless they have a secondary bacterial infection, as the rash will go away on its own.
Treatments such as OTC corticosteroid cream, calamine lotion oatmeal baths, and oral antihistamines can help relieve itching, as can applying cool, wet compresses several times a day..
Clinicians may wish to prescribe oral corticosteroids for patients with widespread rash and large numbers of blisters. Antibiotics should be prescribed if a secondary bacterial infection occurs.
Counsel patients about the appearance of plants including poison ivy, poison oak and poison sumac and remember the phrase, “Leaves of three, let them be.”
Poison ivy is a weed-like plant that can grow as a bush, plant or thick tree-climbing vine. The plant has three leaves to a stem, and leaves can have smooth or jagged edges and may produce small greenish flowers and off-white berries.
Related plants, including poison oak and poison sumac belong to the same family as poison ivy, and cause similar skin reactions as they contain the same allergen – urushiol.
Advise patients to stay on paths when walking in wooded areas, and to wash skin and clothing immediately if they believe they’ve come into contact with poison ivy. Rash can be avoided if the skin is cleansed with soap and water within 10 minutes after exposure, but will likely penetrate the skin if let be any longer.
1. Freedberg IM, Isin AZ, Wolff K, et al. Fitzpatrick’s Dermatology in General Medicine (5th ed.). 1999. New York: McGraw-Hill.