Sensitization to different pollens and allergic disease in 4-year-old Swedish children

Background Although the relationship between sensitization to different inhalant allergens in adolescents and adults has been intensively studied, information concerning sensitization in children is scarce in particular to pollens. Objectives In 4-year-old children to elucidate the pollen immunoglobulin (IgE) antibody profile (birch only, timothy only and combinations of three pollens (birch, timothy or mugwort) and to relate the results to other inhalant and food allergens, as well as the presence of allergic diseases. Methods A total of 2551 4-year-old children belonging to a prospective birth cohort, which has been followed longitudinally (BAMSE), were investigated with respect to IgE antibodies to pollen and other inhalant and food allergens, and expression of allergic disease, based on questionnaire data. Results Eleven percent (n=285) of the children were sensitized to pollen. Birch was the dominating cause of pollen sensitization (birch sensitization only, n=133); followed by timothy grass pollen (n=56) and a combination of two (n=64) or three (n=30) pollens. A remarkably high proportion of the children sensitized only to birch was also sensitized to other inhalant allergens. This was not seen for children sensitized only to timothy. The highest frequencies of IgE reactivity to food were found in the group of children sensitized to the combination of birch, timothy and mugwort pollen. Children sensitized to timothy only, exhibited symptoms of allergic disease significantly less frequently compared with children sensitized to birch only. Sensitization to birch pollen was found to be closely associated with rhinitis and eczema compared with asthma. The highest frequency of asthma and/or rhinitis and/or eczema was reported in children sensitized to at least two pollens. Conclusion Our results demonstrate that birch is the dominating source of pollen sensitization at the age of four in Sweden. This might associate with the pattern of sensitization to other inhalant and food allergens as well as influence on the expression of allergic disease in this particular age group.