Oral allergy syndrome (OAS) in pollinosis patients after eating pistachio nuts: two cases with two different patterns of onset.

We describe two uncommon cases of oral allergy syndrome (OAS) after eating pistachio nuts (p.n.) in subjects (a 54-year-old man and a 3-year-old girl) with exclusive skin prick test (SPT) positivity to Parietaria (P.) and pistachio nut (p.n.) allergens. Serologic P.- and p.n.-specific IgE determinations were also carried out. A double-blind, placebo-controlled food challenge (DBPCFC) was performed, for ethical reasons, only in the adult patient, but we observed a positive intraoral reaction only after slight scratching of the oral mucosa. Since this patient had put three whole p.n. with their shells into his mouth, breaking them with his teeth, before the onset of symptoms, we suggest that slight injury of the oral mucosa may enhance the local response. Preliminary results with SDS-PAGE and immunoblotting demonstrate the occurrence of a slight degree of cross-reactivity between these allergens, but further studies are necessary to obtain a definite conclusion.