The SchoolNuts study by a team of scientists found that having early-onset eczema, being male, having an Asian background, and a family history of allergic disease all increase the risk of adolescent food allergy.
“We have shown in the current analysis that adolescents with a family history of eczema or hay fever have a two-fold risk of having food allergy in adolescence, whereas family history of asthma was not predictive of adolescent food allergy,” said the researchers.
The study further found that for those with more allergic family members, the risk increased. It also found that when both parent and sibling had food allergy, the risk of adolescent allergy increased.
The study also reinforced that there is still a male predominance of food allergy in 10- to 14-year olds.
Strong Asian link to food allergies
Being an Australian study, it also showed that parent ethnicity and the timing of migration to Australia from Asia were associated with food allergy in adolescents.
“This has previously been reported in both infants and five- to six-year-old children from the same region, and the persistence of this association with adolescent food allergy is a new finding,” said the researchers.
The previous HealthNuts study involving infants showed that peanut allergy and egg allergy at the age of one were both three times more likely for infants with parents born in East Asia compared with infants whose parents were born in Australia.
The report said this was followed by another Australian study among children at school entrance, that reported that compared with children with Australian-born mothers, parent-reported nut allergy was more common in children with Asian-born mothers when the child was born in Australia, but less common in children with Asian-born mothers when the child was born in Asia.
“Environmental factors such as cultural differences in exposure to allergens, in utero factors, unmeasured socioeconomic factors, genetic factors, and the gene-environment interaction are hypothesised to have a role in this ethnicity or migration effect, which is discussed in more detail in our previous publications,” said the team.
“The greater presumed maternal effect we found in the SchoolNuts study suggests that factors that are more strongly influenced by the mother, such as the prenatal environment or diet of the child, may be particularly important.”
The researchers said that eczema, especially when early in onset, was a strong risk factor for adolescent food allergy, which is consistent with findings from studies in early childhood.
The researchers stated, from their findings, if the rise in food allergy prevalence is to be reversed, “targeting early life modifiable factors will be essential”.
Strengths and limitations of the study
The SchoolNuts study was a questionnaire survey among 10- to 14-year-old adolescents and their parents, followed by clinic evaluation including oral food challenge when food allergy was suspected from questionnaire response. A total of 4,991 adolescents were involved.
The nature of the study may have yielded high accuracy in its findings. The report states that the strengths of the study are the large population-based data set and the thorough clinic evaluation that included oral food challenge to confirm allergy diagnosis.
Furthermore, they added that this is the first population-based study to extensively examine demographic, environmental, as well as childhood risk factors for adolescent food allergy.
Nevertheless, they admit that one limitation of this study is the reliance on retrospective recall for reporting various exposures such as the history of early life pet exposure or the age of eczema development, that may result in recall bias.
This method also limited the collection of early life data such as the timing of food introduction in infancy, which has recently been identified as a risk factor for food allergy development.
Source: The Journal of Allergy and Clinical Immunology: In Practice
DOI: https://doi.org/10.1016/j.jaip.2017.12.011
“Risk Factors for Food Allergy in Early Adolescence: The SchoolNuts Study”
Authors: Mari Sasaki et al.