Clinical Cross Reactions Between Anacardiaceae

The prevalence of food allergies has increased in recent decades, ranging from 1 to 3% of the general population. According to international literature and French national surveys, nuts today represent a group of allergens often associated with severe allergic reactions. They are responsible for 18 to 40% of deaths from food-related anaphylaxis.

Among all nuts, the prevalence of anacardiac allergies (mainly cashew and pistachio) continues to increase and has become a growing public health problem. Today, global production is estimated at 4.9 million tonnes of cashews and 1.1 million tonnes of pistachios. The resulting increased exposure may explain the increased prevalence of allergic reactions reported to these fruits. In addition, anaphylactic reactions to anacardiaceae are reported to be even more severe than those occurring in subjects allergic to peanuts.

Cashews and pistachios are known to exhibit immunological cross-reactions with one another. In fact, they have a strong sequential homology between their storage allergens Ana o 1 / Pis v 3 (7S vicilin, 78% homology); Ana o 2 / Pis v 2 (legume 11S, 80% homology) and Ana o 3 / Pis v 1 (albumin 2S, 70% homology). For this reason, some authors talk about the cashew / pistachio syndrome and associate the two allergenic sources by considering them as one, in clinical practice.

The diagnosis of allergy to nuts, and therefore to anacardiaceae, is based on a compatible clinical history, the presence of specific IgE (demonstrated by positivity to realistic skin tests and serum IgE assay), and positivity on the oral food challenge test.

In clinical practice, taking into account the cashew / pistachio syndrome, when the allergy work-up for cashew is negative, allergists tend to advise to reintroduce pistachio at home, considering the two allergens as sufficiently homologous to authorize such a practice. In this context, the investigators decided to check whether this practice, which is based mainly on in vitro homologies, is risk-free, based on the clinical experience of our center.