Probiotics: use in allergic disorders: a Nutrition, Allergy, Mucosal Immunology, and Intestinal Microbiota (NAMI) Research Group Report.

The underlying denominators and treatment targets in allergic disorders may be outlined as aberrant barrier functions of the skin epithelium and gut mucosa and dysregulation of the immune response to ubiquitous environmental antigens. Dietary methods to control symptoms and reduce the risk of allergic disease have hitherto focused on elimination diets, alone or in combination with other environmental measures. The results have not been satisfactory regarding long-term prevention, and new approaches are urgently needed. Realization of this, together with the demonstration that the immunophysiologic regulation in the gut depends on the establishment of the healthy gut microbiota, has led to the introduction of novel modes of therapeutic intervention on the basis of the consumption of monocultures and mixed cultures of beneficial live probiotic microorganisms. The current aims of intervention are to avert deviant microbiota development, strengthen the gut barrier function, and alleviate abnormal immune responsiveness. Specific probiotics, selected from members of the healthy intestinal microbiota most of them belonging to Lactobacillus or Bifidobacterium, aid in degradation/structural modification of enteral antigens, regulation of the secretion of inflammatory mediators, and direction of the development of the immune system during the critical period of life when these functions are immature and inexperienced and the risk of allergic disease is heightened. In humans, documented effects have been reported for alleviation of intestinal inflammation, normalization of gut mucosal dysfunction, and down-regulation of hypersensitivity reactions, thereby preferentially targeting allergic conditions with intestinal involvement. The probiotic performance of strains differs; each probiotic strain is a unique organism itself with specific properties that cannot be extrapolated from other, even closely related, strains. Moreover, it would seem simplistic to assume that a single supplementation would suffice to counter the plethora of allergic disease. First, it needs to be acknowledged that a more profound understanding of the complex nature of allergic disorders is needed, as it is likely that there are distinct etiologic factors and pathogenetic mechanisms underlying the heterogeneous manifestations. Second, host-related factors influence the probiotic effects; the distinction in the antiallergic potential of probiotics can be explained by the age of the host and the habitual diet with other potentially active compounds and their conceivable joint probiotic effects. Therefore, research activities are currently focusing on identification of specific strains with immunomodulatory potential, and on the question how the food matrix and dietary content interact with the most efficacious probiotic strains or specific strain combinations.