Allergy to pistachio: crossreactivity between pistachio nut and other Anacardiaceae.

Background: Anaphylaxis against Anacardiaceae nuts is uncommon and the allergens involved still poorly characterized. For this reason two patients with allergy towards pistachio nut (a member of the Anacardiaceae family) have been studied.

Objective: Identification of immunoallergens present in pistachio nut and analysis of crossreactive antigens in other members of the same plant family, specifically cashew and mango.

Methods: Presence of specific IgE for pistachio and cashew nut and for mango seed and pulp was determined by skin tests and radioallergosorbent assay (RAST). The allergenic profile of pistachio and cashew was analyzed by sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) followed by immunoblotting. Crossreactivity between pistachio and the other Anacardiaceae was studied by RAST inhibition.

Results: Skin tests were positive for pistachio and cashew in the two children and for mango seed in one. RAST was positive for pistachio and cashew in both patients. On immunoblotting, serum from both patients recognized several pistachio and cashew allergens with a molecular weight ranging from < 14.2-70 kDa. RAST inhibition demonstrated common antigenic determinants between pistachio and cashew nut. Crossreactivity was also found between pistachio nut and mango seed but not with mango pulp.

Conclusion: Pistachio nut contains several protein allergens able to trigger type I hypersensitivity reactions. These allergens can be found also in cashew nut and mango seed but not in mango pulp.