Age-dependent tendency to become sensitized to other classes of aeroallergens in atopic asthmatic children

Background: Several longitudinal studies report that allergic sensitization increases with age from childhood to adulthood. Objective: To evaluate whether an age-dependent tendency to become sensitiz ed to new classes of allergens is present in atopic children, we studied re trospectively the changes in allergic sensitization in 165 asthmatic patien ts, monosensitized (ie, sensitized to only one class of allergens) in the f irst survey, Methods: All the children (18 months to 8 years at enrollment), attended ou r outpatient clinics twice, at time intervals ranging from 2 to 10 years. O n each visit, sensitization to house dust mites, pollens, animal danders, a nd molds was determined by skin prick test. Results: We found that 43.6% (n = 72) of the patients became polysensitized on the second survey. According to age on first survey, the patients were further divided into two age groups: (I) group I = 18 months to <5 years ol d (n = 98) and (2) group 2 = 5 to 8 years (n = 67). The transition from mon osensitization to polysensitization observed in the entire population was p resent in both groups: 47 (47.9%) of the 98 children in group 1 and 25 (37. 3%) of the 67 children in group 2 showed to be sensitized to more classes o f allergens, as compared with first survey. Both in the whole population an d in the two age subgroups, the changes in the frequency of monosensitizati on between the two evaluations were time-dependent (P <.05, each Chi(2)). F inally, to investigate whether monosensitization to a specific class of all ergens could favor the development of polysensitization, we evaluated the f requency of polysensitization in the second survey in patients originally m onosensitized to house dust mites or to pollens. We found that of the 130 p atients originally monosensitized to house dust mites, 59 became polysensit ized (45.4%), while of the 28 patients originally monosensitized to pollens , 9 became polysensitized (32.1%) (P >.1). Similar results were obtained wh en patients were divided into age groups. Conclusion: These data demonstrate that (I) monosensitized children are lik ely to become polysensitized and (2) house dust mite sensitization and, at a lower degree, pollen sensitization, apparently seem to play a "triggering " role in the development of polysensitization, since a high proportion of children originally monosensitized to house dust mites or to pollens became polysensitized.