Scientific Study

Peanut allergy is one of the most common food allergies in childhood. In vitro cross-sensitization between peanut and tree nuts (TN) is high, but only a subgroup of patients allergic to peanut will have a concomitant allergy to one or several TN. In this article, the authors report a case of a 12-year-old boy who experienced 1 episode of lips and mouth itching, generalized urticarial, and eyelid angioedema 20 minutes after ingestion of peanut at 4 years of age. The immunoallergological study revealed the presence of a concomitant allergy to peanut, pistachio, and cashew confirmed with medically supervised oral food challenges (OFC) in a child who had never eaten these TN. The mechanism of IgE-mediated hypersensitivity was demonstrated by positive skin prick tests (SPT) with commercial extracts, although the specific IgE (sIgE) for these foods was negative. As described in the literature, we concluded that serum peanut and TN sIgE measurements have lower sensitivity than SPT to assess IgE sensitization, and OFC is the gold standard for accurate diagnosis of food allergy. We highlight the relevance of excluding or confirming TN allergy in a peanut-allergic patient who had never ingested certain TN, and of knowing the clinical relevant cross-reactivity patterns between TN, pistachio/cashew, and walnut/pecan, that could reduce the need for OFC in clinical practice, reducing allergy rates and financial and health burdens of food allergy. https://doi.org/10.5415/apallergy.0000000000000109