Background The association between salivary IgA levels and development of allergy is controversial and the employed methodology has been questioned.
Objective The aim of the study was to relate the levels of total IgA, SIgA and allergen-specific IgA antibodies in saliva to the development of allergy in infants during the first 2 years of life.
Methods Saliva samples from 80 infants participating in a prospective study regarding the development of allergy were collected at 3 or 6, and 12 and 24 months of age. Total IgA, SIgA and Fel d 1 and β-lactoglobulin specific IgA levels were analysed with ELISA.
Results The levels of total IgA and SIgA increased with age. The number of samples with detectable IgA to Fel d 1 tended to increase with age, whereas the opposite was observed for IgA to β-lactoglobulin. Infants who developed allergy tended to have higher levels of total IgA, and allergen-specific IgA was more commonly detected than in non-allergic children. In contrast, non-allergic children tended to have higher levels of SIgA. Furthermore, the levels of SIgA were higher in sensitized infants with no allergic symptoms than in sensitized children with symptoms. Infants with allergic parents had lower SIgA levels than infants without. Direct exposure to cat and cow's milk did not influence the levels of allergen-specific IgA levels, nor was there any association between breast-feeding and IgA production.
Conclusion The kinetics of food and inhalant allergen-specific IgA in saliva during the first 2 years of life is similar to what has earlier been shown for IgG in serum. Development of allergy tended to be associated with high levels of total and allergen-specific IgA antibodies, but low levels of SIgA. Furthermore, high levels of SIgA seemed to protect sensitized children from developing allergic symptoms during the first 2 years of life, supporting a possible protective role of SIgA against development of allergy.