Poison ivy (Toxicodendron) dermatitis
- Lori Prok, MD
Lori Prok, MD
- Assistant Professor of Dermatology and Pediatrics
- University of Colorado Denver School of Medicine
- Thomas McGovern, MD
Thomas McGovern, MD
- Private Practice
- Fort Wayne, IN
- Section Editors
- Robert P Dellavalle, MD, PhD, MSPH
Robert P Dellavalle, MD, PhD, MSPH
- Section Editor — Dermatology
- Professor of Dermatology and Public Health
- Denver VA Medical Center, University of Colorado School of Medicine and Colorado School of Public Health
- Daniel F Danzl, MD
Daniel F Danzl, MD
- Section Editor — Environmental Emergencies
- Professor of Emergency Medicine
- University of Louisville School of Medicine
- Joseph Fowler, MD
Joseph Fowler, MD
- Section Editor — Dermatitis
- Clinical Professor of Dermatology
- University of Louisville School of Medicine
Exposure to plants of the Anacardiaceae family account for more allergic contact dermatitis than all other plant families combined. In the United States, the most important members of this family are those of the genus Toxicodendron (previously classified as in the genus Rhus [1,2]), which include common or northern poison ivy (Toxicodendron radicans), western poison ivy (Toxicodendron rydbergii), eastern poison oak (Toxicodendron toxicarium), western poison oak (Toxicodendron diversilobum), and poison sumac (Toxicodendron vernix). Toxicodendron means "poisonous tree," an appropriate choice for these dermatitis-provoking species. In contrast, although they often have three-leaflet configurations similar to those of Toxicodendron, members of the genus Rhus are nonallergenic [1,2]. Throughout this topic review, we refer to Toxicodendron dermatitis by the common name "poison ivy dermatitis."
This topic reviews the epidemiology, prevention, and treatment of allergic contact dermatitis due to these Toxicodendron species. The evaluation and management of contact dermatitis from other causes is discussed separately (see "Overview of dermatitis", section on 'Contact dermatitis'). Despite the prevalence of poison ivy dermatitis in the United States, there are very few well-designed, published studies examining the management of this condition.
Many people are sensitized to urushiol, the allergenic compound found in poison ivy, poison oak, and poison sumac. Fifty percent of people will react to poison ivy in nature, and approximately 75 percent will react to patch testing with urushiol. Annually, an estimated 25 to 40 million Americans require medical treatment after exposure [3,4]. Firefighters, forestry workers, and farmers constitute a large proportion of the victims affected through occupational exposure, and this can have important occupational and economic impacts [4,5].
Poison ivy dermatitis affects all ethnicities and skin types, and most geographical regions in the United States are at risk  (see 'Geography' below). Children are also affected; most children over the age of eight years are sensitized . Allergic responsiveness to poison ivy appears to wane with age, especially in those with mild reactions and limited sensitizing exposures.
IDENTIFYING THE PLANT
While the common phrase "leaves of three, let them be" is a helpful reminder to avoid poison ivy and related plants, members of the Toxicodendron genus have varied presentations based on the season, growth cycle, region, and climate (figure 1 and picture 1A-C) .
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- IDENTIFYING THE PLANT
- CLINICAL PRESENTATION
- Barrier creams
- Topical symptomatic therapy
- Topical corticosteroids
- Systemic corticosteroids
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS
- Epidemiology and identification
- Pathogenesis and clinical presentation
- Prevention and treatment