Microbial products in allergy prevention and therapy.

Epidemiological and experimental studies have led to the hypothesis that stimulation of the immune system by certain microbial products may prevent or treat allergic diseases (1–5). There are also bacterial products on the market which have been proposed for treatment of allergic diseases but their clinical efficacy is not well documented, however. The European Academy of Allergology and Clinical Immunology (EAACI) appointed a Task Force to critically evaluate available information on the potential use of microbial products in allergy prevention and therapy and to discuss guidelines for future research. This first position paper is separately assessing the effects of bacterial extracts, probiotics, mycobacteria, oligodesoxynucleotides (ISS-ODN), and lipopolysaccharide derived molecules in allergic diseases. The section for each of the listed products is structured to present the alleged rationale that would justify their use against allergy and experimental data supporting it. Then, the outcome of representative clinical trials are summarized with regard to efficacy and safety (Table 1). Finally, conclusions are made regarding their potential role in allergic diseases and the eventual need for further research. As this is a very dynamically evolving field, the EAACITask Force will keep monitoring the new developments and will upgrade this position paper at regular intervals. Bacterial extracts