Allergen skin test reaction patterns in children (≤10 years old) from atopic families suggest age-dependent changes in allergen-IgE binding in early life

Background: Genetic studies of atopy rely upon evidence of abnormal IgE production, usually elevated total IgE or skin prick test (SPT) reactions. However, these measures may change with subject age. Methods: We screened 1,099 members of atopic families (aged 6-87 years) by serum total IgE and SPT for 14 allergens. For those SPT negative, we screened for Amb a 1- and Der p 1-specific IgE. Der p 1 IgE-Der p 1 allergen binding affinities were done on randomly selected subjects. Results: There were significantly fewer atopics ≤10 years old (69.1%) compared to those >10 years old (75.8%) based upon any SPT-positive result. Children ≤10 years had fewer SPT-positive reactions and smaller SPT wheal reaction areas. Yet, mean total IgE values were comparable to those of the older group. Screens for specific IgE showed no differences in proportions of atopics (≤10 years old = 83.1% and >10 years old = 82.3%). Among those SPT-positive for house dust mite extract, there was a positive correlation between Der p 1 binding affinity and the wheal area of the house dust mite extract. There was a positive correlation between the number of SPT-positive reactions and total IgE for both age groups. However, there was only a significant relationship between SPT-positive wheal area and total IgE for those >10 years old and no apparent relationship between wheal area and total IgE for those ≤10 years old. Conclusion: These results suggest that atopy-specific physiological mechanisms, primarily those involving allergen-IgE binding, change during the earliest years of life.