Development of allergy and IgE antibodies during the first five years of life in Estonian children.

Background: Epidemiological studies have demonstrated a low prevalence of allergic diseases and atopic sensitization among schoolchildren and young adults in the formerly socialist countries of Central and Eastern Europe as compared to Western Europe.

Objective: The aim of our study was to prospectively investigate IgE responses to food and inhalant allergens and the development of allergy during early childhood in a population with a low prevalence of atopic disorders.

Methods: In a population-based prospective study, 273 children were followed from birth through the first 5 years of life, recording manifestations of allergy by questionnaires and clinical examinations at 0.5, 1, 2 and 5 years (n = 213). Skin prick tests (SPT) were performed using natural foods (cow's milk, egg white) and commercial extracts of inhaled allergens (cat, dog, D. pteronyssinus, birch, timothy). In addition, serum IgE levels and circulating IgE antibodies against the seven allergens were determined.

Results: The prevalence of allergic diseases at 5 years of life was 19%. Atopic dermatitis was the most common allergic disease at all ages. The point prevalence of positive skin prick tests was 7% at 0.5, 1 and 2 years of age, and 3% at 5 years. Circulating IgE antibodies against food allergens were common at all ages, i.e. 13, 23, 36 and 36%, respectively, at 0.5, 1, 2 and 5 years. The prevalence of circulating IgE antibodies to inhalant allergens increased from 1.5% at 0.5 years to 11% at 1, 19% at 2 and 47% at 5 years. The antibody levels were generally low, however. The value of positive SPT and the presence of IgE antibodies in the diagnosis of clinical allergy were low.

Conclusion: The results of this prospective study carried out in a previously socialist country with a low allergy prevalence among schoolchildren and young adults indicate that transient sensitization in early childhood is followed by a down-regulation of skin reactivity.