When given to infants who had trouble tolerating cow's milk, a new probiotic not only banished the allergy, but also changed the composition of their gut bacteria significantly.

Babies treated with the probiotic had bigger colonies of several strains known to produce butyrate and other short chain fatty acids that help maintain homeostasis in the gut.

"The ability to identify bacterial strains that could be used as novel therapeutics for treating food allergies is a fundamental advance," says co-author Jack Gilbert, PhD, of the University of Chicago.

In the past decade, food allergies have risen by as much as 20 percent in certain geographic areas of developed countries, and cow's milk is particularly problematic, according to the paper, published in The ISME Journal.

Widespread antibiotic use, reduced exposure to infectious diseases, Caesarean birth and formula feeding in addition to a diet richer than ever in processed foods are all factors thought to alter the once-happy equilibrium between the gut and its bacteria.

For individuals who may be genetically susceptible to allergies, skewing the composition of the microbes in the gut can be the straw that breaks the camel's back, according to the researchers.

Previous research demonstrates that formula that contains the milk protein casein and supplemented with the species Lactobacillus rhamnosus GG (LGG) helps infants to develop a tolerance to cow's milk.

In the new study, the researchers performed sequence analysis to identify the composition of bacteria found in stool samples they collected from healthy babies, those who were allergic to cow's milk but had been fed the LGG formula, and those who had been fed regular formula.

Gut bacteria composition was vastly different between healthy babies and those with cow's milk allergies, according to the paper.

Babies who developed a tolerance to cow's milk as a result of being fed the LGG probiotic formula had higher levels of butyrate-producing bacteria than those for whom the probiotic formula did not banish the allergy.

This links tolerance of problem foods with acquiring specific strains of gut bacteria, possibly narrowing down the pool to the butyrate-producing Blautia and Coprococcus.

"Translating these findings into clinical treatments is our next goal, and one that is now possible through the new FARE Clinical Network center here at the University of Chicago," says Gilbert.

In July of this year, University of Chicago Medicine was selected by the Food Allergy Research and Education (FARE) to join its FARE Clinical Network, dedicated to finding a cure for life-threatening food allergies.