Can prebiotics help prevent allergy?

In April 2014, Lucina reported on studies supporting the use of probiotics in infants to prevent allergic symptoms (doi.org/10.1136/archdischild-2014-306137), and in November 2017 Archivist featured the PPOIT trial (doi.org/10.1136/archdischild-2017-314082), where a probiotic helped induce peanut tolerance in allergic children. Probiotics are the ‘good’ bacteria, usually lactobacillus species, which are supposed to change the gut microbiome in an immunologically favourable way. Prebiotics are specific food substances, usually oligosaccharides, which provide a favourable substrate for probiotic bacteria to flourish in the gut, and should therefore produce the same benefits. There is less good evidence for the effectiveness of prebiotics, and a review has set out to look at what there is (Guello-Garcia C et al. Clin Exp Allergy 2017. doi: 10.1111/cea.13042). The authors, working for the World Allergy Association (WAO), found 22 studies describing randomised controlled trials of prebiotics in infants, and none investigating their use in pregnant or breastfeeding mothers. The prebiotics used were mostly fructo-oligosaccharides and galacto-oligosaccharides, given with standard formula milk. Most infants were not breastfed. Together these showed a modest benefit in preventing eczema (RR 0.68; 95% CI 0.4 to 1.2), wheeze/asthma (RR 0.37; 95% CI 0.2 to 0.8), and food allergy (RR 0.28; 95% CI 0.1 to 1.0). …