Gut bacteria in babies could lower allergy and asthma risk, scientists say

Researchers say a natural gut substance may calm allergic reactions early in life.

Cute baby boy eating alone while seating in high chair in dining room at home

Published: January 26, 2026 at 3:52 PM

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Allergies and asthma are on the rise among children, and many parents are left wondering if there is anything they can do early on to reduce the risk. Now, scientists at the Technical University of Denmark (DTU) say the answer may lie in babies’ gut bacteria.

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A major international study has found that infants who are colonised early with specific types of bifidobacteria are less likely to develop allergies and asthma later in childhood. These naturally occurring gut bacteria produce a substance that appears to calm the immune system and reduce overreactions to allergens.

The findings, published in the journal Nature Microbiology, could help shape future strategies for preventing two of the most common chronic conditions affecting children worldwide.

The research suggests that supporting a baby’s gut microbiome in the first months of life may have long-lasting benefits for immune health.

Why gut bacteria matter in early life

The study followed 147 children from birth until the age of five, tracking their gut bacteria, immune responses and the development of allergies or asthma.

Researchers found that babies who developed a high level of certain bifidobacteria early in life were exposed to beneficial metabolites produced by these microbes. One compound in particular, called 4-hydroxyphenyl lactate, or 4-OH-PLA, stood out for its ability to dampen allergic immune responses.

Project leader Susanne Brix Pedersen, professor at DTU Bioengineering, says identifying how this process works is a crucial step forward.

The key breakthrough is that we have now identified a specific mechanism that can suppress the development of allergic reactions in the immune system already during infancy.

Professor Susanne Brix Pedersen, DTU Bioengineering

The science behind allergies and IgE

To understand the impact of 4-OH-PLA, the researchers carried out laboratory experiments using human immune cells.

They discovered that natural levels of the substance reduced the production of immunoglobulin E (IgE), the antibody that plays a central role in allergic reactions, by around 60 percent.

When allergens such as pollen or food proteins enter the body, IgE antibodies bind to them and trigger immune cells, leading to symptoms such as itching, eczema, hay fever and, in some cases, asthma. Higher IgE levels are strongly linked to an increased risk of developing allergic disease.

Crucially, the researchers found that 4-OH-PLA lowered IgE without affecting the production of other important antibodies, suggesting it works in a targeted and balanced way.

Data from thousands of samples across three countries

The findings are based on extensive data from three large birth cohorts in Sweden, Germany, and Australia.

Researchers analysed stool samples from infants to map gut bacteria and metabolite levels, using genetic testing and small-molecule analysis. Blood samples were also taken to measure IgE antibodies linked to food and airborne allergens.

The final step was testing the mechanism directly in human immune cells, where 4-OH-PLA was shown to inhibit IgE production.

Together, the results show a clear biological link between certain bifidobacteria, the substances they produce and healthy immune development in early childhood.

Birth, feeding, and early contact all play a role

overhead view of three babies lying with their heads together on a blanket

The team also looked at what increases the chances of babies developing these beneficial gut bacteria in the first place.

Rasmus Kaae Dehli, specialist in systems immunology at DTU Bioengineering, explains that birth method and early feeding are key factors.

It is remarkable that children born vaginally were 14 times more likely to acquire the bifidobacteria from their mothers.

Rasmus Kaae Dehli, DTU Bioengineering

Exclusive breastfeeding and early contact with other young children were also linked to higher levels of these bacteria.

However, the researchers note that modern lifestyles mean many infants are not colonised with these microbes, making additional preventive approaches important.

Could this lead to new prevention strategies?

The researchers believe their findings could open the door to new ways of preventing allergies and asthma.

Future options may include probiotic supplements, infant formula enriched with specific bifidobacteria, or even adding 4-OH-PLA itself. The aim would be to support the immune system during the critical window in the first months of life, when immune development is most sensitive.

Brix Pedersen is already involved in the BEGIN study at Aarhus University Hospital, which focuses on early prevention of asthma and allergies. In this study, one of the beneficial bifidobacteria identified in the research is being given to infants.

If those trials show positive results, Brix Pedersen estimates that a preventive strategy for young children could be available within a few years. Treatments for people who already have allergies or asthma would take longer, potentially up to ten years, due to the need for drug development and clinical trials.

If we can translate this knowledge into a preventive strategy – for example, through probiotic supplements or enriched infant formula—it will be a major step forward in the fight against allergies and asthma, which currently affect millions of children worldwide.

Brix Pedersen

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For parents, the research adds to growing evidence that early gut health plays a powerful role in shaping long-term wellbeing, and that tiny microbes may make a big difference.

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