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

agk's Library of Common Simple Emergencies

Presentation
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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, partic- 
ularly 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:
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- Have the patient apply cool compresses of 
    Burow's solution (Domeboro Powder Packets 2 
    packets in 1 pint of water) for 20-30 
    minutes every 3-4 hours (more often if 
    comforting).
- Small areas can be treated 2-3 times per day, 
    enhanced at night with an occlusive plastic 
    (Saran) wrap dressing.
- Diphenhydramine (available over the counter 
    as Benadryl) or Hydroxyzine (Atarax) 25mg 
    po q6h will help mild itching between 
    application of compresses.
- Tepid tub baths with Aveeno colloidal oatmeal 
    (one cup in 1/2 tub) or cornstarch and 
    baking soda (1 cup of each in 1/2 tub) will 
    provide soothing relief.
- When there is involvement of the face, in 
    severe reactions or in situations where the 
    patient's livelihood is threatened, early 
    and aggressive treatment with systemic 
    corticosteroids should be initiated. 
    Prednisone (60-80mg a day tapered over 2 
    weeks) will be necessary to prevent a late 
    flare-up or rebound reaction. One 40mg dose 
    ot intramuscular triamcinolone acetonide 
    (Kenalog) will be equally effective.

What not to do:
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- Do not try to substitute pre-packaged steroid 
    regimens (Medrol Dosepak, Aristopak). The 
    course is not long enough and may lead to a 
    flare up.
- Do not allow patients to apply fluorinated 
    corticosteroids such as Topsyn or Valisone 
    indefinitely to the face, where they can 
    produce premature aging of the skin.
- Do not institute systemic steroids in the 
    face of secondary infections such as 
    impetigo, cellulitis, or erysipelas. Also, 
    do not start steroids if there is a history 
    of tuberculosis, diabetes, herpes or severe 
    hypertension.

Discussion
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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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