Allergic contact dermatitis induced by poison ivy. In the Intermountain West, we have a type of poison ivy that has three leaves connected centrally, and they have slight serration on the edges of the leaves. An old adage is "leaves of three, let them be." Often the lesions of poison ivy are linear, and can consist of redness and swelling, or redness and blistering. If there is very much localized inflammation, the dermatitis can generalize as diffuse redness and scaling on areas that were not exposed to the allergen. This is called autoeczematization. Areas of poison ivy dermatitis are best treated with an ultra-potent topical steroid twice daily, or prednisone, 1 mg/kg per day until the eruption resolves; this usually takes about three weeks.
