Objective: In this mixed-methods study, we aimed to identify the food allergen with the greatest reported burden to families with preschool and school-aged food allergic children. Methods: Parents of children with 2+ food allergies responded to an online, anonymous study on the burden of multiple food allergies. We used descriptive statistics and thematic analysis to analyze the quantitative and qualitative data, respectively. Results: A total of 123 parents participated. The 4 most prevalent food allergies among preschoolers (preschoolers 0-5 years: N = 46; 37.4%) were egg (78.3%), milk (69.6%), peanut (60.9%) and tree nut (54.3%). These were also the most common allergies among school-aged children school-aged 6-18 years; N = 77; 62.6%), albeit in different proportions. Milk was reported as the most stressful food allergy in childcare centers (71.9%), whereas parents of school-aged children reported more comparable distributions of the most stressful food allergy at schools. Qualitatively, we identified one theme per age group: “Peanut is easy to avoid, but milk is everywhere” for preschoolers, and “Every food allergy for school-aged children.” Conclusions: The burden associated with types of food allergy differs between preschool and school-aged children.