These are believed to have altered the mutually beneficial relationship between humans and the bacteria that live in the gastrointestinal tract. This dysbiosis, or distorting of the structure of the microbial community, can cause allergies in those who are genetically prone to developing them.

It seems increasingly likely that modern environmental influences, including widespread antibiotic use, high-fat and low-fiber diets, reduced exposure to infectious diseases, Cesarean birth and formula feeding are factors.

The National Institute of Allergy and Infectious Diseases note that allergy to cow’s milk is common in infants and young children and can develop within days to months after birth. Symptoms include abdominal pain, hives and eczema , or colic and sleeplessness, as well as blood in the stool and poor growth, depending on the type of immune response involved.

The Centers for Disease Control and Prevention (CDC) name allergies as the sixth leading cause of chronic illness in the US, affecting more than 50 million Americans and costing more than $18 billion annually in health care. In a study released by the CDC in 2013, food allergies among children increased by 18% from 1997 to 2007 and by 50% between 1997 and 2011.

Teams from the University of Chicago, IL, Argonne National Laboratory in Lemont, IL, and the University of Naples Federico II in Italy found that some infants gained tolerance to cow’s milk after being treated with probiotic formula, while others did not.

Food allergies are growing in prevalence in developed countries, and 3% of children globally are allergic to cow’s milk. New research carried out on children with cow’s milk allergy has shown that structural differences in gut bacteria may be the reason why some children do not acquire tolerance.

In previous research, Roberto Berni Canani and colleagues from the University of Naples studied the reaction of infants with cow’s milk allergy to probiotic and nonprobiotic formula. One group was given a formula containing a form of the milk protein casein, supplemented with the probiotic bacterial species Lactobacillus rhamnosus GG (LGG). The other group was treated with a nonprobiotic formula.

Fast facts about allergies 5.6% of children in the US have a food allergy

10.6% of children have a respiratory allergy

12% have a skin allergy. Learn more about allergies

Those who took the probiotic formula developed a higher level of tolerance, suggesting that probiotic formula is more helpful in overcoming cow’s milk allergy.

For the new study – published in The ISME Journal – a team led by Cathryn Nagler, PhD, Bunning food allergy professor at the University of Chicago, investigated the relationship between probiotic treatment and gut bacterial composition to see if it would increase tolerance to cow’s milk.

To do this, sequence analysis was used to identify bacteria in stool samples collected from three groups: healthy infants without allergy, infants with cow’s milk allergy who had been fed the LGG enriched probiotic formula, and those who had been fed the formula without added probiotics.

Overall, the gut microbiome of infants with a cow’s milk allergy was significantly different to that of the healthy control group, suggesting that differences in the bacterial structure do influence the development of allergies.

Of those infants who were fed the probiotic formula, some developed tolerance to cow’s milk while others did not.

Those who developed tolerance were found to have higher levels of certain strains of bacteria, specifically the type that produce short-chain fatty acids, such as butyrate. These bacteria help to control the internal conditions (homeostasis) in the gut.

Dr. Nagler and her team identified a common class of mucus-associated gut bacteria that are instrumental in regulating how dietary allergens reach the bloodstream. They now believe that the way commensal bacteria regulate allergic responses to food may be different than what was previously thought.

The findings suggest that certain bacteria make children more likely to develop tolerance, and that tolerance is linked to the acquisition of specific strains of bacteria, including Blautia and Coprococcus, which produce butyrate.

Jack Gilbert, PhD, associate professor in the Department of Ecology & Evolution at the University of Chicago, group leader for microbial ecology at Argonne National Laboratory and co-author of the study, says:

“The ability to identify bacterial strains that could be developed as a way to therapeutics for treating food allergies is a fundamental advance. Translating these findings into clinical treatments is our next goal.”

Last year, Medical News Today reported on a study showing that children living in inner cities are more likely to develop food allergies than those in rural environments.