A study conducted in 2008 by the Sahlgrenska Academy at the University of Gothenburg says diet may be the culprit.
In Västra Götaland County in western Sweden, half of all teenagers are considered affected by asthma, nasal symptoms and eczema, almost 10 percentage points higher than when a similar study was conducted in 2000.
Who is least affected? Those who eat more fish and butter.
"We want to explore whether there is a connection between diet and allergies, and also whether there are differences between different groups in terms of allergies. If there are, our findings can help direct certain measures to where they are needed the most," says Karin Engdahl (Social Democrat), Chairman of the Public Health Committee, Region Västra Götaland.
Girls also had more allergies than boys, the survey noted.
"The increased general level of skin and airway sensitivity calls for measures to create healthy indoor environments, primarily in schools but eventually also in the young people's future workplaces. There is also a need for information to children, youth and parents, such as medical educational and vocational counselling in schools," says Jonas Brisman, chief physician and project leader of the study at the Section of Occupational and Environmental Medicine, Sahlgrenska Academy, University of Gothenburg.
Two more reports connected to the study are forthcoming; one later this autumn on dietary habits and one in 2010 on health from a socio-economic perspective.