Acute tree nut-triggered food protein-induced enterocolitis syndrome in two infants: a case report.

Introduction: Food protein-induced enterocolitis syndrome (FPIES) is a non-IgE-mediated food allergy characterised by delayed repetitive vomiting and can be difficult to distinguish from infectious illness or even an IgE-mediated allergy. Tree nuts are uncommon but increasingly recognised triggers, and evidence regarding atypical FPIES with concomitant IgE sensitisation remains limited. Case presentation: We describe two infants with severe acute reactions to tree nuts who were managed at a paediatric allergy centre. The first, a boy with eczema and cow's milk allergy, developed reproducible delayed vomiting, pallor, and lethargy after cashew ingestion; an oral food challenge (OFC) confirmed atypical FPIES to cashew and required treatment with intravenous fluids, anti-emetics, and corticosteroids. The second, a girl with eczema and a complex allergic phenotype, had IgE-mediated peanut allergy, FPIES to egg and walnut, and presumed atypical FPIES to cashew. Her reactions were characterised by repetitive vomiting, pallor, lethargy, and hypotension with loss of consciousness, requiring intravenous fluid resuscitation. In both cases, interpretation of the symptoms was challenging due to concomitant infections. Conclusion: These cases add to the limited literature on tree nut-triggered FPIES, illustrate the complexity of atypical FPIES when sensitisation coexists, and highlight challenges in allergen introduction, OFC timing, and management of infants with multiple food allergies.