Reactions to food may affect all age groups in the population and the symptoms may vary from mild itching in the upper respiratory system to severe, life threatening systemic reactions like anaphylactic shock. Reactions to food will be changing at all times since allergy to different foods may arise and disappear in a single individual. In addition, food habits are changing and import of new foods may introduce new allergens. It is therefore important to survey the adverse reactions to food to identify the most common allergens, to be able to revise the food-labelling directive and to secure safe food for individuals suffering from food allergy.
To increase the knowledge of food allergy in Norway, the Norwegian National Reporting System and Register of Severe Allergic Reactions to Food “the Food Allergy Register” was established in 2000. The Register is a collaboration between the Veterinary Institute and the Norwegian Food Safety Authority, whereby the Norwegian Institute of Public Health is responsible for the registry and the daily operation. Cases of severe reactions to food are reported by first-line doctors on a one-page form. Blood or serum samples of the patient may be sent together with the form for analyses of specific IgE-antibodies to a panel of food allergens. Specific IgE to pollen allergens are also analysed since plant foods in general often have similar or homologous allergen sequences that may cause cross-reactions. By the end of 2015 the Food Allergy Register had received 1470 reports.
Results from the Food Allergy Register show increased prevalence in sensitization (i.e. that the patients have specific IgE-antibodies in their serum) to hazelnut, peanut and birch pollen from 2000 to 2015. Analysis of the birch pollen-homologues in hazelnut and peanut, the so called recombinant allergens, or single allergens, show that the increase is largely due to cross reactions caused by primary allergy to birch pollen. It has been registered a change over time in the age distribution of the reported patients up to 2015. The age groups showed two peaks at 0 to 5 years and 21 to 35 years up to 2008, changing to only one group in early childhood (0-5 years) up to 2015. The four most common foods the children are sensitised to have changed from being egg >, milk >, hazelnut and >peanut, to equal number of children being sensitized to peanut and egg, then hazelnut and milk as the third and fourth most common allergen. The 6 year olds and older used to be most often sensitized to hazelnut and peanut, with celery and shrimp as the third and fourth most common foods causing sensitisation. In 2015, hazelnut and peanut are still the most frequent cause of sensitization, but wheat and celery have increased to be the third and fourth most common food allergens, respectively. Reactions to fish are seldom reported. The gender distribution of the 1470 submitted reports has been constant over the years and is 40: 60 men: women and the opposite for the small children where the distribution is close to 70: 30 boys: girls.