Original article Global map of the prevalence of symptoms of rhinoconjunctivitis in children: The International Study of Asthma and Allergies in Childhood (ISAAC) Phase Three Phase One of the International Study of Asthma and Allergies in Childhood (ISAAC) study (1) demonstrated major worldwide variations in the prevalence of symp- toms of asthma, rhinoconjunctivitis and eczema in children (2–5). The International Study of Asthma and Allergies in Childhood Phase One involved more than 700 000 children: 257 800 6- to 7-year olds from 91 centres in 38 countries and 463 801 13- to 14-year olds from 155 centres in 56 countries. Phase One found substantial worldwide variations in the prevalence of reported symptoms of rhinoconjuncti- vitis in children, with up to 25-fold variations in 13- to 14- year olds (4). For both age groups, the lowest prevalence values were found in parts of Eastern Europe and in Southern and Central Asia. In the older age group, low prevalence values were found in China and Portugal. In centres of higher prevalence, there was a greater variabil- ity between the two age groups in the proportion of rhinoconjunctivitis labelled as hay fever (4). Ecological studies using the ISAAC Phase One data were subsequently undertaken and identified that eco- nomic development (6), dietary factors (7), climate (8), infections (9) and pollens (10) may be associated with some of the worldwide variation observed in the preva- lence of symptoms of rhinoconjunctivitis. The International Study of Asthma and Allergies in Childhood Phase Two involved a more detailed investigation of possible etiological factors in 9- to Background: Phase One of the International Study of Asthma and Allergies in Childhood (ISAAC) measured the global patterns of prevalence and severity of symptoms of rhinoconjunctivitis in children in 1993–1997. Methods: International Study of Asthma and Allergies in Childhood Phase Three was a cross-sectional survey performed 5–10 years after Phase One using the same methodology. Phase Three covered all of the major regions of the world and involved 1 059 053 children of 2 age groups from 236 centres in 98 countries. Results: The average overall prevalence of current rhinoconjunctivitis symptoms was 14.6% for the 13- to 14-year old children (range 1.0–45%). Variation in the prevalence of severe rhinoconjunctivitis symptoms was observed between centres (range 0.0–5.1%) and regions (range 0.4% in western Europe to 2.3% in Africa), with the highest prevalence being observed mainly in the centres from middle and low income countries, particularly in Africa and Latin America. Co-morbidity with asthma and eczema varied from 1.6% in the Indian sub-continent to 4.7% in North America. For 6- to 7-year old children, the average prevalence of rhinoconjunctivitis symptoms was 8.5%, and large variations in symptom prevalence were also observed between regions, countries and centres. Discussion: Wide global variations exist in the prevalence of current rhinocon- junctivitis symptoms, being higher in high vs low income countries, but the prevalence of severe symptoms was greater in less affluent countries. Co-mor- bidity with asthma is high particularly in Africa, North America and Oceania. This global map of symptom prevalence is of clinical importance for health professionals. N. Aït-Khaled 1 , N. Pearce 2 , H. R. Anderson 3 , P. Ellwood 4 , S. Montefort 5 , J. Shah 6 , and the ISAAC Phase Three Study Group* 1 International Union Against Tuberculosis and Lung Disease, Paris, France; 2 Centre for Public Health Research, Massey University Wellington Campus, Wellington, New Zealand; 3 Department of Community Health Sciences, St GeorgeÕs, University of London, London, UK; 4 Department of Paediatrics: Child and Youth Health, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand; 5 Department of Medicine, University of Malta, Malta; 6 Jaslok Hospital & Research Centre, Mumbai, India Key words: allergic; co-morbidities; conjunctivitis; global epidemiology; income; rhinitis. Prof. Nadia Aït-Khaled, MD International Union Against Tuberculosis and Lung Disease (The Union) Head of Asthma Division 68, Boulevard Saint-Michel 75006 Paris France *The members of the ISAAC Phase Three Study Group are listed in Appendix. Accepted for publication 19 July 2008 Allergy 2009: 64: 123–148 Ó 2008 The Authors Journal compilation Ó 2008 Blackwell Munksgaard DOI: 10.1111/j.1398-9995.2008.01884.x 123