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PROBIOTICS have been defined as live micro-organisms which when administered in adequate amounts confer a health benefit on the host. The suggested health benefits of probiotics are many, including modulation of the immune system. Modulation of the immune system, as well as other health effects, are strain specific and can thus not be extrapolated from one strain to another. Within immune modulation, probiotics have in particular been investigated for their effect on allergies. It appears that probiotics have limited effect on allergies in adults, but some successes have been reported. Consumption of a dairy product fermented with Lactobacillus paracasei Lactobacillus paracasei Lpc-37, Lactobacillus acidophilus 74-2 and Bifidobacterium lactis 420 has been shown to reduce the severity of atopic dermatitis in adult sufferers. More studies have been performed with children. But, also here, success in the treatment of allergies has been variable. A combination of e.g. Lactobacillus rhamnosus HN001 and B. lactis HN019 has been found to reduce atopic eczema, but only in children with food allergies. The varying success with which probiotics have been used in the treatment of allergic diseases relates probably in part to the use of different strains; probiotic health benefits are strain specific. But it may also be that once an allergy has developed, probiotics can no longer redirect towards a more tolerant immune response. The best opportunities may therefore be in populations at-risk of developing allergies. Children from parents with allergies have approximately 50% risk of developing atopic dermatitis. Feeding of probiotics to these children from birth onwards might redirect the development of their immune system into a more tolerant direction. Studies that have been performed indicate actually that feeding of the probiotic to the expectant mother should already start a few weeks before birth. A number of studies have shown that such a strategy may lead to reduction in atopic dermatitis by approximately 50% (i.e. some 25% of the at-risk population develops atopy). Such benefits appear to persist for many years after the intervention stopped. Also here, the effects are strain specific. This has clearly been shown in the only study to compare two different probiotic strains in parallel in such a setting. L. rhamnosus HN001 was found to reduce the incidence and severity of atopic dermatitis whilst B. lactis HN019 did not. Interestingly, both strains influenced the immune profile of the mothers' breast milk and in cord blood; suggesting a mechanism by which antenatal probiotic feeding may influence the allergy risk in newborns. Potential mechanisms
What are the potential mechanisms behind the probiotic functionality in the management of allergies? The so-called hygiene hypothesis suggests that a reduction in exposure to infectious agents and incidence of infectious diseases could be the cause of the ever-increasing prevalence of allergies. At birth, the immune system is immature and requires 'training'. This training is naturally provided by challenges with microbial exposure. This theory is strongly supported by epidemiological evidence. Children raised on farms with livestock have dramatically reduced risk for developing allergies, compared to the general population. Actually, even consumption of raw (unpasteurised) milk reduces the risk. After the reunification of West and East Germany, it was clear that there was a significantly higher incidence of allergies in the former then in the latter populations despite a comparable genetic background. Similar observations were made when comparing Finnish and Russian Karelian populations, which also have a similar genetic background. Here, too, the formeNEW BALANCE