A Rare Case of Systemic Reaction to Carrot Due to PR-10 in a Young Child.

Background: Pollen-Food Allergy Syndrome (PFAS) typically presents as mild oral symptoms but can rarely progress to systemic reactions. Pathogenesis-related proteins group 10 (PR-10) are proteins usually associated with oral allergy syndrome due to their thermolabile and gastrolabile properties. Case Presentation: We report a 12-year-old boy with birch pollen allergy who developed anaphylaxis after raw carrot consumption without identified cofactors. Previously, he experienced only oral allergy syndrome with raw carrot and fennel. Molecular diagnostics confirmed isolated PR-10 sensitization. The reaction occurred during birch pollen season, and the patient tolerated cooked carrot, consistent with PR-10's thermal instability. Conclusions: This case highlights how PFAS, typically characterized by mild and localized symptoms, can occasionally manifest with systemic reactions. High levels of specific IgE for Bet v 1 and pollen season may represent risk factors for systemic reactions in PFAS patients. Clinicians must be aware that allergies due to pollen cross-reactive allergens can be associated with systemic reactions.