The Enquiring About Tolerance (EAT) study found:

• Babies who had eczema at three months and one year of age showed a higher abundance of a bacterium called Clostridium sensu stricto, compared to those without eczema
• Babies born by caesarean section had a significantly less diverse gut flora, compared to those delivered by normal birth
• The early introduction of allergenic foods (cow’s milk, egg, wheat, peanut, sesame and cod fish) from three months accelerated the development of greater gut bacteria diversity, compared to exclusive breastfeeding

The bacterial flora of the gut plays an important role in the development of the human immune system in early life. The EAT study investigated how the infant gut flora evolves during infancy, in particular in relation to hygiene factors, eczema, food allergy and the introduction of solids.

The study, funded by the British Skin Foundation, was led by a group of researchers from King’s and Guy’s and St Thomas’ NHS Foundation Trust, with collaborators from the National Institute of Health (USA), St George’s London, and the University of Manchester.

In the study 1,303 exclusively breastfed infants from England and Wales were enrolled in a dietary intervention study from three months of age. Stool samples were collected at enrolment, six and twelve months to study the evolution of their gut microflora. All participants were also examined for eczema and food allergies until three years of age.

Six foods (cow’s milk, egg, wheat, sesame, peanut, and cod fish) were introduced into infant diets alongside breastfeeding, and compared to exclusive breastfeeding until six months of age. The study found the early introduction of these allergenic solids from three months accelerated the development of greater gut bacteria diversity, compared to exclusive breastfeeding.

Although all babies in the study were exclusively breastfed until enrolment at three months of life, the types of bacteria in the gut varied, with infants having either a gut flora rich in bacteria called Bifidobacteria, Bacteroides or Escherichia/Shigella.

He added: “We hope these findings improve our understanding of the role our gut microbiome plays in the development of the immune system from an early age.”

Dr Tom Marrs, consultant in paediatric allergy at Evelina London Children’s Hospital, which is part of Guy's and St Thomas', said: “We also examined a long list of hygiene related factors and whether they additionally influenced the bacterial gut flora during the first year of life. These factors include mode of baby delivery, receiving antibiotics and being exposed to pets and farm animals, as well as the number of siblings. Out of all of these factors, the only strong signal was that those who were born by caesarean section had a reduced diversity in their gut flora, most likely because vaginal delivery exposes us more to microbes from our mothers.”

Professor David Gawkrodger, British Skin Foundation trustee and consultant dermatologist, said: “The British Skin Foundation is delighted to have funded this important research study into the role of the gut microbiome in the development of eczema and food allergies in early life.

“Since there seems to be a relationship between the type of bacteria in the gut and the development of eczema, the manipulation of the gut bacteria in early life might reduce the likelihood of eczema in babies predisposed to develop it."