Age-, Sex- and Region-Specific Patterns in Sensitization Rates to Food Allergens and Food Allergy Prevalence in Croatian Children: The H2020 IMPTOX and ERDF P4 Study Findings

<b>Background/Objectives:</b> Food allergy (FA) is a substantial health burden in children. FA is often associated with malnutrition and malabsorption, due to restrictive food avoidance diets, which can significantly impair the patient's and their family's quality of life. To this date, population-based data combining sensitization and clinical allergy remain limited. This study aimed to assess the patterns of sensitization rates to food and food allergy prevalence rates in Croatian children and to evaluate differences according to age, sex, and region of origin. <b>Materials and Methods:</b> In this cross-sectional study, 1948 preschool and school-aged children from three Croatian regions (Zagreb, Dalmatia, and Slavonia) were included. Participants underwent skin prick testing to common food and inhalant allergens. Data on personal and family medical history were collected using questionnaires and medical records. FA prevalence was evaluated using self-reported data in school-aged children and physician-diagnosed FA data in preschool children. <b>Results:</b> Overall, 41% of participants were sensitized to at least one allergen, while 13% were sensitized to at least one food allergen. Tree nuts-particularly hazelnut-were the most common food-derived sensitizers, followed by hen's egg, cow's milk, and fish. Boys exhibited higher total sensitization rates than girls (44.2% vs. 37.5%; <i>p</i> = 0.001), higher food allergen sensitization rates (14.7% vs. 11.4%; <i>p</i> = 0.037), and higher total polysensitization rates (30.7% vs. 22.6%; <i>p</i> < 0.001). School-aged children showed higher total sensitization (44.8% vs. 33.4%; <i>p</i> < 0.001) and polysensitization rates (29.8% vs. 20.5%; <i>p</i> < 0.001) than preschool children, while sensitization to food allergens did not differ between age groups. Food allergen sensitization rates differed by region, with higher prevalence in Zagreb compared with Dalmatia and Slavonia (<i>p</i> = 0.0055), whereas total sensitization rates did not differ regionally. The agreement between sensitization and self-reported FA among school-aged children was low (κ = 0.22; <i>p</i> < 0.001), as was the agreement between sensitization and physician-diagnosed FA in preschool children (κ = 0.13; <i>p</i> < 0.001), despite high specificity in both analyses (95% and 99%%, respectively). <b>Conclusions:</b> Allergic sensitization is common among Croatian children, but it poorly predicts clinically relevant food allergy. These findings highlight the multifactorial nature of allergen sensitization in children and emphasize the need for improvements in diagnostic pathways, targeted prevention strategies, and continued surveillance to optimize allergy prevention and management in children.