Cashew nut

Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 1999.

Common name: Cashew nut tree
Botanical name: Anacardium occidentale
Family: Anacardiaceae
Origin: Originally native to tropical Americas but is now grown in most tropical climates.
Description:  
Uses: The nut is edible. Modified cashew shell nut oil has a number of industrial uses including an ingredient in ink, as an adhesive and in the manufacture of resin.
Allergens: The cashew shell nut contains a brown oily juice, full of very potent allergens including cardanol, cardol and anacardic acid.
Allergy: There are two problems with cashew nuts, allergy to cashew nut shell oil and allergy to the nut itself. Roasting the shell of the nut liberates irritating vapours, but if roasting is complete, all the allergens should be inactivated. Problem arise when children play with the raw shells, if improperly shelled cashew nuts are sold, or roasting is incomplete.
There are a number of reports of allergic contact dermatitis following ingestion of cashew nut butter, a cashew nut pesto, and cashew nuts contaminated with cashew nut shell oil. Most reactions appear to have only been dermatitis (although most needed treatment with high doses of oral steroids).
This is quite different to the IgE-mediated immediate anaphylaxis to cashew nut. This potentially life-threatening condition is due to an allergic reaction to a very small molecular weight component of the kernel itself. This appears to cross react with pistachio nuts. Fortunately allergy to cashew nut appears to be much less common than to other tree nuts.
Cross reactions: These cross react to other members of the Anarcardaciae family including poison ivy, Toxicodendron succedaneum (Rhus tree) and mango.
Other information:  
Patch test:  

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