OBJECTIVE: The relation of viral infections and allergic diseases is inconclusive. The objective of the analysis therefore was to examine the relation between immunoglobulin levels and sensitization to common allergens as measured by the skin prick test (SPT). Methods: In a population-based study of 2,470 children, 2,188 skin prick tests, and 2,042 blood samples could be analyzed. RESULTS: At least one positive SPT was observed in 19.2% of the children. IgA und IgG levels did not show any association with SPT response. As expected, there was a sharp increase in the two highest quartile groups of IgE (p for trend <0.0001), while the prevalence of positive SPT continuously decreased with higher IgM levels (p for trend 0.002). This effect of IgM could be seen for all allergens examined. If an upper respiratory tract infection was reported one week prior to testing, the prevalence of a positive SPT was also reduced by nearly one half, however, this association was not significant. CONCLUSIONS: Since IgM has a half-life of approximately 5 days, the inverse association found between IgM and the prevalence of positive SPT seems to be a transient effect of a prior infection.