A 64-year-old man presents for evaluation and treatment of an itchy rash involving his chest and extremities. The eruption began 2 days earlier. He lives in Pennsylvania and denies recent travel. The patient notes that he walks his dog daily in wooded areas. He is on antihypertensive medications, but none were recently started. Examination reveals multiple erythematous 2- to 4-mm papules and vesicles around the affected sites. Numerous excoriations are noted on his legs.
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Poison ivy, poison sumac, and poison oak are common causes of contact dermatitis in the continental United States. Poison ivy is found in all 50 states except California, Alaska, and Hawaii. Poison sumac is found throughout the East Coast and southern states.1 There are 2 varieties of poison oak: Western Poison Oak, which is native to the Pacific Northwest and California, and Easter Poison Oak, which is found throughout the East Coast (except Pennsylvania), southern states, and some Midwestern states and Texas.1
Up to 75% of the US population are clinically sensitive to these noxious plants,2 which pose an environmental hazard to those who work in, or recreationally enjoy, the outdoors. The primary allergen in these plants is urushiol, which is contained within the plants’ sap. Brushing against the plant or an animal’s fur coated with urushiol induces an allergic reaction in predisposed persons within 24 to 72 hours.3 Itching and at times burning are followed by the appearance of erythema and, in severe cases, vesicles. Symptoms are believed to be caused in part by release of cytokines including interleukin 33.4
Prophylaxis of urushiol-induced dermatitis includes avoidance, protective clothing, and use of barrier creams. Immediate washing of contacted areas with soap and copious amounts of water will prevent or mitigate reaction.5 Untreated, poison ivy lasts on average 2 weeks and the course can be markedly diminished with use of oral and high-potency topical steroids.3
Stephen Schleicher, MD, is director of the DermDox Center for Dermatology in Pennsylvania, as well as associate professor of medicine at Commonwealth Medical College and clinical instructor of dermatology at Arcadia University and Kings College.
1. Where do I find poison ivy, oak, and sumac plants? TecLabs. Accessed April 6, 2021. www.teclabsinc.com/tips-info/guides-how-tos/where-do-i-find-poison-ivy-oak-and-sumac-plants#.
2. Kim Y, Flamm A, ElSohly MA, et al. Poison ivy, oak, and sumac dermatitis: what is known and what is new? Dermatitis. 2019;30(3):183-190. doi:10.1097/DER.0000000000000472.
3. Vaught CK, Mold JW. Poison ivy: how effective are available treatments? J Fam Pract. 2016;65(11):801-809.
4. Liu B, Tai Y, Achanta S, et al. IL-33/ST2 signaling excites sensory neurons and mediates itch response in a mouse model of poison ivy contact allergy. Proc Natl Acad Sci U S A. 2016;113(47):E7572-E7579. doi: 10.1073/pnas.1606608113.
5. Neill BC; Neill JA; Brauker J; Rajpara A; Aires DJ. Postexposure prevention of Toxicodendron dermatitis by early forceful unidirectional washing with liquid dishwashing soap. J Am Acad Dermatol. 2019;81(2):e25. doi: 10.1016/j.jaad.2017.12.081.