Background The association between allergic sensitization and eczema has been debated for years. Objective We sought to determine and compare the strength of the association between allergen skin sensitization and eczema in both developing and industrialized countries. Methods Twenty-eight thousand five hundred ninety-one randomly selected 8- to 12-year-old schoolchildren in 20 countries were physically examined for flexural eczema and received skin prick testing to Dermatophagoides pteronyssinus , Dermatophagoides farinae , cat hair, Alternaria tenuis , mixed tree and grass pollen, and allergens of local relevance. Results The age- and sex-adjusted odds ratios (ORs) for a positive association between flexural eczema and atopy ranged between 0.74 (95% CI, 0.31-1.81) and 4.53 (95% CI, 1.72-11.93), with a significantly stronger association in affluent compared with nonaffluent countries (combined age- and sex-adjusted ORaffluent = 2.69 95% CI, 2.31-3.13 and ORnonaffluent = 1.17 95% CI, 0.81-1.70). The combined population attributable fraction for atopy in flexural eczema was 27.9% for affluent and 1.2% for nonaffluent-country centers. Correlating gross national per-capita income with either ORs or population attributable fractions for atopy in flexural eczema confirmed a highly significant positive association ( P = .006 and P < .001, respectively). Conclusions The association between atopy and flexural eczema is weak and more variable than previously suggested, and the strength of this association is positively linked to gross national income.