Studies on sensitization and atopic disease in infants and children

Abstract: Sensitization to food allergens dominated in infancy and IgE antibodies to inhalant allergens appeared later in a cross-sectional multicentre study of 224 children with atopic disease (113 children aged 0-3 years and 111 children aged 4-15 years). IgE antibodies to peanut, hazelnut, and almond were important in both age groups and even before known ingestion in infancy, suggesting sensitization through breast-milk.A similar pattern of food sensitization in infancy and later appearance ofantibodies to inhalant allergens was seen in 324 children constituting an enlarged group from three different cohorts of children and followed prospectively from birth to age 4 to 15. Antibodies to inhalant allergens developed in 76% of children with IgE antibodies to egg white (EW) in infancy. Of children with inhalant antibodies up to age 12-15, 32 % had previously had antibodies to EW.The possible effects of maternal antigen avoidance during lactation on the development of atopic disease were studied in children with a positive family history of atopy. The mothers of 65 infants avoided eggs, cow's milk and fish during the first three months of lactation, whereas the mothers of 50 infants had no dietary restrictions. (Previous reports from this study had shown significantly less atopic dermatitis (AD) during the first 6 months of life in the diet group, and after that a non-significant trend towards less AJ;:> up to age 18 months.) The present follow-up at age 4 years showed significantly less AD in the diet group, both as cumulative (29 %versus 56 %, p=0.007) and as current prevalence (12 % versus 38 %, p=0.03). The frequencies of asthma and allergic rhinoconjunctivitis were similar, as were the number of sensitized children.Possible effects of an early severe respiratory viral infection on the development of asthma, other atopic symptoms and sensitization were studied in 47 infants hospitalized with respiratory syncytial virus (RSV) bronchiolitis, and their 93 matched controls obtained from the local child health centres. Asthma, up to age 3, was significantly more common in the RSV children (23% versus 1 %, p< 0.001). This was also the case with serisitization at age 3, as measured by skin-prick tests and two screening tests in serum for food and inhalant antibodies (32 % versus 9 %, p=0.002), whereas the frequency of AD was similar in the two groups. The combination of RSV bronchiolitis and a family history of asthma was the most important risk factor for the development of asthma. For sensitization, the combination of RSV bronchiolitis and a family history of atopic disease was the most important risk factor.In a study of 34 infants hospitalized with RSV bronchiolitis, the eosinophil cationic protein (ECP)/albumin ratios in nasal secretions increased during the 6 months following RSV bronchiolitis, suggesting a long-standing inflammatory reaction, which might be important for the high frequency of post-bronchiolitic wheezing. ECP and myeloperoxidase in serum and ECP/albumin ratios in nasal secretions could not be used to predict later asthma or sensitizat:ion.In conclusion, food sensitization dominated in infancy, and antibodies toaeroallergens appeared later. In infants with a family history of atopic disease, the risk of developing atopic dermatitis up to age 4 years was reduced in the group in which the mothers avoided cow's milk, egg and fish during lactation. An early RSV bronchiolitis increased the likelihood of future asthma and sensitization up to age 3 especially if combined with heredity for asthma and atopic disease.