The incidence of allergic diseases has been increasing in industrialized countries during recent years. Although several environmental factors are thought be involved, lack of moderate level of microbial challenges during the infantile period is knownto skew the immune status toward the development of allergic diseases. Various strains of probiotics such as Bifidobacterium, Lactobodllus, and Lactococcus have been assessed for their ability to suppress the occurrence of atopic dermatitis (AD) in animal models and human studies. Although the effect of probiotics on allergic responses is different depending on the strains, doses, and experimental protocols, animal studies generally have shown immunomodulatory activities of probiotics including suppression of specific or nonspecific IgE production, reduction of infiltrated eosinophils and degranulated mast cells, potentiation of regulatory T cell cytokines such as IL-10 and TGF-beta relative to IL-4 and IL-5, and potentiation of Th1/Th2 activity alongwith reduced symptoms of AD. Several well-designed double-blind placebo-controlled human studies showed that some probiotic strains administered during perinatal period prevented the occurrence of AD but could not consistently show a reduction in specific or nonspecific IgE or a change in specific immunomodulatory cytokines. Taken together, published results suggest that the administration of selected strains of probiotics during the perinatal period may be helpful in the prevention of AD.
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