jacobi ambulatory care service toxicodendron: a painful summer institution

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Toxicodendron: A painful summer institution

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A Latin Refresher:

• Toxicodendron means Poisonous Tree• Toxicodendron radicans is Poison Ivy• Toxicodendron toxicarium is Poison Oak• Toxicodendron vernix is Poison Sumac

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Leaves are primarily trifolate

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Urushiol is the allergenic component. It is a kind of oil found in the leaves, stems, and roots.

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It is found in other foodstuffs:

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Urushiol penetrates the epidermis and binds to Langerhans cells. In sensitized patients, previously stimulated helper T cells recognize the urushiol and initiate an immune response.

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Time Course

• Symptoms develop in 4 to 96 hours.• Symptoms can peak up to 2 weeks after

exposure.• The fluid in the blisters is NOT antigenic. The

rash doesn’t spread. Continued infection is due to re-exposure.

• Allergic responsiveness wanes with age, particularly in those with milder reactions.

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More information about urushiol:

• It binds to cell membranes. After an hour or so, it won’t wash off.

• It is stable at high temperatures. So, burning poison ivy or poison oak disperses through the air with it’s allergenic potential intact. It can cause inflammation and irritation of respiratory tissues.

• It is stable in general, and can remain on fomites for a long time. Some say up to 5 years!

• It can waft on a summer breeze and cause a reaction in the very very allergic.

• Some native American tribes use it to remove warts.• Only homo sapiens react to it.

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Looks like:

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Not…

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Complications

• Edema, especially when the face or genitals are affected.

• Respiratory difficulties.• Bacterial super-infection, primarily with gram

positive organisms.

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Treatment

• Calamine lotion and oatmeal baths.• Sedating anti-histamines.• High potency topical corticosteroids. (But not

on mucous membranes or in skin folds.)• Systemic glucocorticoids if: face or genitals

are affected; more than 10% of the body is involved; reaction is severe. Start with 1 mg/kg of prednisone, give it for a week, and then taper over the next two weeks.

• NB: Avoid topical benadryl, which causes a reaction all it’s own.