Rhus Dermatitis

David Effron, MD, and Alex Green, DO

MetroHealth Medical Center, Cleveland, Ohio

A 4-year-old girl presented with the highly pruritic, vesicular rash characteristic of rhus dermatitis. The day before, she had been playing outdoors at her grandmother’s house. No pets were present, and the patient did not recall being stung or bitten by insects. There are bushes infested with poison ivy on the grandmother’s property.

The next morning, a vesicular rash had erupted on the girl’s wrists, posterior knees, and the corners of her mouth. Some of the vesicles ruptured after the girl scratched them. None of the other children with whom the girl was playing had similar symptoms. She had received the varicella vaccine, and she has a history of mild eczema.

At presentation, her vital signs were stable, and she was breathing and swallowing without difficulty. Oral examination revealed a small group of vesicles (0.1-0.2 cm) on the tip of her tongue and an erythematous, dry, crusty rash in the corners of her mouth (A). There was no swelling in the mouth or throat. The vesicles on the wrists (B) ranged from 0.25 cm to 0.5 cm and contained clear fluid. The 0.25-cm fluid-filled vesicles on the backs of her knees formed a linear pattern. The patient had no stridor, and the rest of the physical examination findings were unremarkable.

Rhus dermatitis can be caused by poison ivy, poison sumac, or poison oak. The oil on the leaves, roots, and stems contains urushiol, a highly allergenic compound that can cause a type IV hypersensitivity reaction. Allergic persons are sensitized to the compound before reacting to the oil. Our patient had had a previous case of poison ivy. Because this is a delayed hypersensitivity reaction, the vesicles appear 8 to 72 hours after contact with the plant.

The location of vesicles depends on the site of exposure and whether the oil was transmitted along the skin by a vector, including scratching. Scratching creates a linear pattern. Lesions persist for 10 to 21 days. Vesicle fluid does not contain urushiol; thus, rupturing of vesicles does not cause the rash to spread further. Clothing, tools, and other objects that have been exposed to the oil must be washed because of the continued possibility of transmission.

Because the girl had no secondary infection, her treatment was symptomatic. Management included daily colloidal oatmeal baths, over-the-counter topical lotions, and cold, wet compresses, followed by topical hydrocortisone, 2.5%, to relieve pruritus and swelling. The tongue vesicles were treated with topical anesthetics. More severe cases of rhus dermatitis call for oral corticosteroids taken daily and tapered over a 3-week period.