Background Histamine skin reactivity (HSR, the dimension of the skin weal elicited by histamine 10 mg/mL) is a variable that differs in children from different European countries and increases over time in the same place (Italy).
Objective In this epidemiologic study, we investigated to what extent differences in HSR influence the relationship between positive allergen skin prick tests (ASPTs) and serum-specific IgE concentrations.
Methods Between October 2001 and February 2002, 591 unselected 9–10-year-old schoolchildren drawn from five small towns in central Poland (Starachowice), central Italy (Ronciglione, Guardea) and Libya (Al-Azyzia, near the Mediterranean sea and Samno, 900 km south of the coast) were analysed for histamine, common ASPT and for serum total and specific IgE.
Results HSR differed markedly in children from the three countries (Libya>Italy>Poland) whereas serum total IgE concentrations remained the same. The prevalence of children with measurable serum specific IgE (0.35 kU) or with a positive ASPT for five common allergens was high in Italy, lower in Poland and far lower in Libya. A 3-mm ASPT weal corresponded to a serum-specific IgE concentration that was two to threefold higher in children with low HSR compared with children with high HSR (P=0.008).
Conclusion These findings suggest that HSR – a variable that differs in schoolchildren populations from the three countries studied – independently influences the results of ASPT and its influence should be considered when ASPT are assessed in international studies. The HSR differences found in the populations reported here probably reflect a complex, dynamic, environmental interaction that should be monitored in the different parts of the world.