Abstract
The prevalence of allergic disorders has rapidly increased in the industrialized countries including Japan as well as in the developing countries. Recently, an epidemiological survey in Japan showed that the prevalence of Japanese cedar pollinosis has increased from 16.2% to 26.5% of Japanese population over the past ten years. Reasons such as increased allergens, changed food life habits and nutrients, and environmental deterioration, etc. have been suggested to account for the increased prevalence of allergic disorders. One of the explanations is the “hygiene hypothesis”, which postulates that the decrease of opportunity of exposure to immunostimulating microorganisms in the early childhood as a result of cleanliness trends, vaccination and use of antibiotics, caused the increased prevalence of allergic diseases. Neonates are known to be in a Th2-skewed immune balance and need microorganism-stimulation for the development of balanced immunity. Epidemiological and mechanism studies have indicated the association between tuberuculin response and composition of intestinal microflora with the development of allergies. Numerous human studies have shown that tubercle bacilli and probiotic bacteria, such as lactobacilli and bifidobacteria, are potentially beneficial in the prevention and/or treatment of allergic diseases. However, further studies are needed for demonstrating the efficiency of which strain, what intake timing and what dose for targeted subjects.
