Systemic contact dermatitis to raw cashew nuts in a pesto sauce

Systemic contact dermatitis from the cashew nut shell oil resorcinol allergens cardol and anacardic acid is recognized clinically as a dermatitis with flexural accentuation, typically distributed on the extremities, groin, and buttocks, and occurring generally 1 to 3 days after ingestion of raw cashew nuts contaminated with allergenic oil. We report a case of systemic contact dermatitis to raw cashew nuts, an atypical and unexpected ingredient flavoring an imported pesto sauce. Plants with allergens that potentially cross-react with poison ivy and other Toxicodendrons, and the concepts of systemic contact dermatitis and hyposensitization are reviewed.