A 35 y.o. male has just started a job at a sushi restaurant and comes in with a rash on his hands.

What could cause this?

Our patient had severe dermatitis secondary to urushiol, the active ingredient in poison ivy which causes a rash.  How, you might ask, is this related to working in a sushi restaurant?   Urushiol is also found in the skin of mangoes which the patient had been peeling in the restaurant.  He knew he was very allergic to poison ivy because he had previously worked in landscaping and on several occasions his eyes swelled shut and he required steroids.  He had no idea that mangoes contain the same toxin.  The differential would also include Mycobacterium marinum.

The family Anacardiaceaeare a family of flowering plants containing mango, poison ivy, sumac, and cashews.  The skin of mangos contain urushiol as well as the shells of cashews; which is why cashews are always sold after they are shelled.

Poison ivy is most likely to transmit urushiol in the spring when the shoots are tender and sap is likely to be exposed.  The name urushiol comes from the Japanese “urushi” meaning lacquer  because of the extensive work done on the Japanese lacquer tree in the 1920’s to identify urushiol.   Onethousandth of a milligram of urushiol sap will produce a typical dermatitis.  If poison ivy is burned the urushiol adsorbs to particles of soot and can be inhaled causing lung injury.  Poison ivy leaves have been stored for five years without losing their ability to cause dermatitis.  Even clothing exposed to poison ivy has retained it has  ability to cause dermatitis for one year after washing.

In short

“Leaves of three, let them be.”

Mohr C. The geographical  distribution in North America of poison-ivy and allies.  1925. Am Jour. Bot 12;338-350.

Walter Conrad Muenscher.  Poison Ivy and Poison Sumac. 1930. New York State College of Agriculture Extension Service.  NY State Coll of Agriculture.

Gladman AC. Toxicodendron dermatitis: poson ivy,oak, and sumac. 2006.  Wilderness &Environmental medicine. 17(2): 120-8.