Background:
Classically we have been taught that the skin prick test (SPT) must be performed over 4 years of age mainly because of the lack of sensibility the test has on younger children, now a days the utility of the SPT in younger children with atopic history is controversial and it would help make an early diagnosis. The objective of this study is to describe the prevalence of allergen sensitization in children between 0 and 5 years of age that have atopic history. We also describe the sensitization percentages to the most relevant allergens according to age group.
Methods:
SPT performed between January 2006 and July 2010 at the Respiratory and Allergy Department of Clínica Santa Maria to children with atopic story were analyzed. A standard base of 21 allergens from LETI laboratory was used.
Results:
752 children with SPT were studied; they were divided into 2 groups. Group A corresponding to children between 6 and 24 months of age, group B corresponding to children between 25 months and 5 years of age. In group A 76 SPT and group B 676 SPT were performed. The total number of SPT positive to 1 or more allergens was 46.4%. (Group A: 6.4%, group B 40%). The most prevalent allergens according to age were: group A: grass 16%, egg 16%, cat dander 10% and house dust mite(Dermatophagoides pteronyssinsus and farinae) 10%. Group B: grass 15%, house dust mite 13.6%, fungal allergens (Aspergillus an Alternaria) 11.4%, trees 9% and cat dander 6.6%.
Conclusions:
A high sensitization percentage to grass and egg is seen under 24 months of age. Egg sensitization diminishes significantly over 2 years of age, on the other hand house dust mite and fungal sensitization increases with age which could be explained by a longer exposure time in genetically predisposed children. 46% of the children are sensitized to 1 o more allergens which make us question the classical indication that SPT will be done over 4 years of age. When high suspicion of atopic history, a SPT should be performed independently of patient age.