The prevalence of childhood allergies, such as hayfever, have increased over the past decade in many countries of the world, especially among younger age groups, reveals an article in this week’s issue of The Lancet.

In 1991 researchers carried out the International Study of Asthma and Allergies in Childhood (ISAAC) to assess the worldwide prevalence of asthma, hayfever, and eczema*. Between 2002 and 2003, Innes Asher (University of Auckland, New Zealand) and colleagues repeated ISAAC to examine any changes in prevalence. The investigators surveyed the parents of over 193 400 children aged 6-7 years from 37 countries on the presence of symptoms of asthma and allergies, such as wheezing, in their child. They also asked around 304 680 children, aged 13-14 years from 56 countries, the same questions. Developing countries such as South Africa, Brazil, and Iran and developed countries such as Canada, New Zealand, Sweden, and the UK contributed to the study.

The investigators found that increases in prevalence were more common than decreases and occurred more commonly in the younger age-group. The increases were greatest for eczema in the younger age-group, and for hayfever in both age-groups. However, in the older age group where prevalence of asthma had been previously been high, symptoms of the condition more commonly decreased. The only regions where increases in prevalence of all three disorders occurred more often in both age-groups than decreases were Asia-Pacific and India.

In the UK, where around 1700 children took part in the study, asthma prevalence went up from 18.4% to 20.9%, hayfever from 9.8% to 10.1%, and eczema from 13% to 16% between 1991 and 2003.

Professor Asher concludes: “The data have direct relevance for health-service delivery in the countries included in the study as well as providing a basis for understanding these disorders. In almost all centres, there was a change in prevalence of one or more disorders over time. Although changes in mean annual prevalence to the order of 0.5% might sound small, such changes could have substantial pubic-health implications, especially since the increases took place most commonly in heavily populated countries.”

Contact: Professor Innes Asher, Department of Paediatrics, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand. T) +64 9 373 7599 x86734 .(JavaScript must be enabled to view this email address)