Certain gut bacteria in infants may reduce the risk of developing allergies later in childhood. This is the finding of new research from the ALADDIN study at Karolinska Institutet, published in Nature Microbiology.

During the first few months, a child's gut flora develops rapidly. The study followed children from birth to five years of age to see how early bacteria are linked to allergy antibodies (IgE) in the blood.

The researchers analysed series of faecal samples from children and their mothers using advanced DNA technology and simultaneously measured various lactic acids produced by the bacteria.

The results were clear: children who had high levels of bifidobacteria producing aromatic lactic acids at an early age developed fewer allergy antibodies. One of the most significant was the lactic acid 4-hydroxyphenyl lactate (4-OH-PLA). These children also had a lower risk of atopic eczema at two years of age.

Of the factors that favour the ‘good’ bacteria, three proved to be particularly important: Vaginal delivery, exclusive breastfeeding during the first two months, contact with older siblings early in life. These situations seem to help the protective bifidobacteria establish themselves.

‘The study shows that the presence of the right gut flora early in life can reduce the risk of allergies. If we can find ways to support these bacteria in infants, perhaps through diet, breastfeeding or other methods, this could eventually become a new tool for preventing allergies,’ says Johan Alm, paediatrician and researcher at the Department of Clinical Research and Education, Södersjukhuset, Karolinska Institutet.

In laboratory experiments, the researchers were able to show that the lactic acid 4-OH-PLA reduced IgE production in immune cells by approximately 60 per cent. This suggests that the bacteria are not only ‘present’ but actively influence the immune system.

The study is a collaboration between Karolinska Institutet, Technical University of Denmark and several international research groups. The study was funded by the Swedish Research Council, Region Stockholm and several foundations, among others. The researchers report no conflicts of interest.