Editorial comments on: "Worldwide time trends in prevalence of symptoms of rhinoconjunctivitis in children: Global Asthma Network Phase I".

In the second half of the 20th century, clinical observations led to suspect a strong increase in allergy prevalence in the Westernized world. However, this had to be confirmed by robust epidemiological studies. Among them, the ISAAC initiative provided unique data from around the world for the prevalence of allergic diseases.1 Although respiratory allergies and atopic dermatitis continued to rise in the last decades, but mostly in developing countries, the focus in Europe, North America, and Australasia has been more on food allergy, as these have been sharply increasing in these countries.2,3 In addition, studies were mostly focusing on the development of respiratory diseases in risk populations and crosssectional studies were largely lacking.4 We highlight here as editor's choice the recent study by Strachan and colleagues, which aimed to update trends in prevalence of symptoms of childhood allergic respiratory diseases and compare them with data from 15 to 23 years ago.5 Data of symptoms suggesting allergic rhinitis and conjunctivitis by standardized questionnaires were collected from over 100,000 participants. Centers were located in India, Mexico, and various countries in Africa, SouthEast Asia, and in Europe and South America. Although the authors discovered a substantial heterogeneity between the countries and the regions of the world (between less than 10% and up to 25%), they found overall that the prevalence of symptoms of allergic rhinoconjunctivitis were no longer increasing in children.