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11.01 Rhus (Toxicodendron) Contact Dermatitis (Poison Ivy, Oak, or Sumac)


Presentation

The patient is troubled with a pruritic rash made up of tense vesiculo-papular lesions on a mildly erythematous base. Typically these are found in groups of linear streaks and may be weeping, crusted, or confluent. If involvement is severe, there may be marked edema, particularly on the face and periorbital and genital areas. The thick protective stratum corneum of the palms and the soles generally protect these areas. The patient is often not aware of having been in contact with poison ivy, oak, or sumac but may recall working in a field or garden from 24 to 48 hours before the onset of symptoms.

What to do:

What not to do:

Discussion

Poison oak and poison ivy are forms of allergic contact dermatitis that result from the exposure of sensitized individuals to allergen in sap. These allergens induce sensitization in more than 70 percent of the population, may be carried by pets, and are frequently transferred from hands to other areas of the body in the first few hours before the sap becomes fixed to the skin. The gradual appearance of the eruption over a period of several days is a reflection of the amount of antigen deposited on the skin and the reactivity of the site, not an indication of any further spread of the allergen. The vesicle fluid is a transudate, does not contain antigen, and will not spread the eruption elsewhere on the body or to other people. The allergic skin reaction usually runs a course of about 2 weeks which is not shortened by any of the above treatments. The aim of therapy is to reduce the severity of symptoms, not to shorten the course.

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from Buttaravoli & Stair: COMMON SIMPLE EMERGENCIES
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Craig Feied, MD
Mark Smith, MD
Jon Handler, MD
Michael Gillam, MD