Asthma and allergies in children could be prevented by altering the type of microbes inside their gut as babies, researchers have suggested.

The team found that a particular pattern of gut microbes in babies just a month old was linked to an increased risk of them developing asthma and allergic reactions as they grew up.

“Early-life intervention may be a strategy by which we can offset allergic asthma in perhaps a portion of the population,” said Susan Lynch, co-author of the research from the University of California, San Francisco, adding that such interventions could include supplementing young babies with a cocktail of bacteria and other microbes lacking in their gut.

According to Asthma UK, the UK has one of the highest rates of asthma symptoms in children in the world, with one in 11 currently receiving treatment for the condition. While the disease can be managed, there is currently no cure.

Writing in the journal Nature Medicine, Lynch and colleagues describe how they analysed the gut microbes of 130 babies aged around one month old by examining their stool samples. They then followed up on the health of the children at two and four years of age.

Microbes such as bacteria and fungi are passed from mothers to babies during birth, while breastfeeding, the surrounding environment and the use of antibiotics are also thought to influence the mix.

The researchers found that the babies fell broadly into one of three groups, based on the mix of microbes living in their gut.

One of the groups, composed of 11 babies, were three times more likely to have allergic reactions at two years and asthma at four years old compared to the other groups.

The stools of these babies, Lynch added, had low levels of bacteria including Faecalibacterium and Bifidobacterium and high levels of fungi such as Candida and Rhodotorula. That raises the possibility of manipulating the mix of gut microbes early in development to reduce the risk.

To unpick how the microbes could affect the likelihood of developing allergies and asthma, Lynch and colleagues exposed immune cells from healthy adults to sterilised stool samples from the lowest and highest-risk babies. The upshot was that samples from the high-risk babies triggered an immune response and suppressed cells involved in keeping allergic responses in check.

That, says Lynch, “[suggests] that the microbes in the gut and their products in these highest-risk children drives an allergic response from very early infancy”.

The researchers also delved into possible explanations for why some babies had the problematic set of gut microbes, finding that those children were more likely to be boys and to grow up in a household without a dog.

Benjamin Marsland, an expert on the impact of microbes on the immune system from the University hospital of Lausanne in Switzerland, described the new research as “important”.

“There is a growing awareness that events very early in life can shape how our immune system matures, and as a consequence, our susceptibility to, or protection against, allergies,” he said.

The new research, he adds, is a stepping stone towards new ways of tackling asthma and allergies. “If we can ensure that a baby is exposed to the right microbes early in life, we might be able to reduce the global burden of allergic diseases, such as asthma,” he said.

But William Cookson, professor of genomic medicine at Imperial College London, urged caution, noting the small number of children considered to have asthma or allergy in the study and that an increase in allergic reactions at two years of age was not found using conventional definitions.

“Asthma is a disease of the airways, it is not a disease of the bowel, and the airways have their own microbiota – fungi and bacteria – which are very, very plainly abnormal in asthmatics,” he added. “So the more logical thing to do, to me, is to look at the lungs, rather than to look at the bowels.”

Dr Erika Kennington, head of research at Asthma UK, said: “We know that gut bacteria can influence our health in many different ways, including determining our risk of developing asthma, but we don’t yet know exactly how this process works.

“This new research helps us better understand the link between gut bacteria and asthma in young children and, in the future, could potentially help us to identify youngsters at higher risk of developing asthma and develop treatments to help them manage it.”

Lynch adds that early life gut bacteria are not likely to be the whole story. “My personal view is that there are many ways to develop the disease,” she said.