A study on hypersensitivity to the basic foods milk, egg, fish and wheat among young school children showed that reported food hypersensitivity was eight times more common than allergies confirmed by allergy tests. This according to a new dissertation at Umeå University in Sweden.
"Most children with allergies to basic foods will develop tolerance before school age. It is therefore important to recurrently evaluate if the child's suspected or proven allergy has disappeared," explains Anna Winberg, doctoral student at the Department of Clinical Sciences and author of the dissertation.
"Parents might have been advised to exclude certain foods from the child's diet due to suspected hypersensitivity in the child during its first year of life. However, this elimination diet often continues until the child reaches 11-12 years of age, without the 'food allergy' having been evaluated. Many school children, therefore, remain on an elimination diet although it is no longer necessary, which can lead to a lower intake of important nutrients."
The study covered all school children at the ages 7-8 years in the municipalities Luleå, Piteå and Kiruna. The results showed that ongoing food allergy actually was rare in children who avoided basic foods due to perceived hypersensitivity. The study showed:
- Reported food hypersensitivity at the age of 7-8 was common (21%) and in a follow-up study at the age of 11-12, the prevalence had increased to 26%.
- Reported allergy to basic foods was eight times higher (5%) than the prevalence of allergy confirmed by allergy tests (0.6%).
- Despite that 14.5% of children at the age of 11-12 years reported that they fully or partly avoided milk due to perceived hypersensitivity, only 3% of these children had an ongoing milk allergy.
- Children with ongoing or outgrown milk allergy had a lower body mass index (BMI) compared to children who did not avoid milk.
There is no exact data available on the prevalence of food allergies in Sweden but an estimated figure of around 5-8% of children and 3-5% of adults are affected. Younger children with food allergies are often allergic to basic foods, milk in particular. Older children and adults are more often allergic to nuts, fish and shellfish. It has been previously shown that the majority of children allergic to basic foods become tolerant, often before school age.
"The results of this study show how important it is with correct allergy diagnoses and to recurrently evaluate children's food allergies to avoid unnecessary elimination of food," says Anna Winberg.
The study also examined biomarkers in blood and stool samples in relation to the outcome of the allergy tests, also called food challenges. Some of the analysed biomarkers showed promising results as potential, future prognostic markers of an ongoing food allergy. These results, however, need further validation by future studies.
About the study:
The study was conducted as a joint project between the OLIN studies (Obstructive Lung Disease in Norrbotten) and Umeå University. In 2006, all school children at the age of 7-8 in the three municipalities Luleå, Kiruna and Piteå were invited to participate in the study, which covered a parental questionnaire with questions on asthma, rhinitis, eczema and food allergies. 2,585 children (96%) participated. When the children were 11-12 years of age, a follow-up using the same methods was performed together with a measurement of BMI. The participation was equally high in the follow-up study in 2010. Children with a reported food allergy were invited to clinical trials and blood tests. Children who were categorised as having a current food allergy were then tested further with a double-blind placebo-controlled food challenge.
Anna Winberg comes from Umeå in northern Sweden. Apart from her doctoral studies at the Department of Clinical Sciences, Anna works as a paediatrician at the Child and Adolescent Clinic at the University Hospital of Umeå.