| Summary: | Background: The prevalence of reported food hypersensitivity among children has increased in Western countries. However, the prevalence varies largely due to differences in methods used in different studies. Double-blind placebo-controlled food challenge (DBPCFC) is the most reliable method to verify or exclude food hypersensitivity. The use of double-blind food challenges is increasing in clinical praxis, but since the method is time- and resource consuming it is rarely used in population-based cohort studies. There is a lack of knowledge on how adolescents and mothers experience participation in double-blind placebocontrolled food challenges and to what extent the food is reintroduced after a negative challenge. While several studies have described the impact of IgEmediated food allergy on Health-Related Quality of Life (HRQL), few studies have described HRQL among children with other food hypersensitivity phenotypes. Aim: The aim of this thesis was to estimate the prevalence of reported food hypersensitivity, associated risk factors, and symptom expressions among schoolchildren. We also examined HRQL among children with total elimination of cow's milk, hen’s egg, fish or wheat due to food hypersensitivity as a group compared with children with unrestricted diet, and after we categorised the children with eliminated foods into different phenotypes of FHS. Finally, adolescents' and mothers' experience of DBPCFC was examined as well if the food had been reintroduced. Methods: Three studies were based on the Obstructive Lung Disease in Northern Sweden (OLIN) paediatric cohort II. The cohort was recruited in 2006 when all children in first and second grade (7-8 years) in three municipalities in Norrbotten were invited to a parental questionnaire study and 2,585 (96% of invited) participated. The questionnaire included questions about food hypersensitivity, asthma, rhinitis, eczema and possible risk factors. The children in two municipalities were also invited to skin prick testing with 10 airborne allergens, and ...
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