A new study has found that problems with gut bacteria could lie behind four major — and very different — childhood allergies.
Eczema, hay fever, asthma and food allergies afflict more than a third of people worldwide.
They are also increasing, with researchers blaming everything from shifting diets to overemphasizing hygiene.
But in a study published on Tuesday in Nature Communications, Canadian researchers suggested another possible cause: disorders in the communities of tiny organisms living within the human gut.
“Developing therapies that change these interactions during infancy may therefore prevent the development of all sorts of allergic diseases in childhood, which often last a lifetime,” pediatrics professor Stuart Turvey of the University of British Columbia said in a statement.
The findings suggest that all four conditions share a common cause that had long escaped notice, coauthor Charisse Petersen of UBC said.
Because the symptoms of each condition are so different — from the respiratory distress of asthma and hay fever to the skin inflammation of eczema and the life-threatening response to food allergies — “researchers tend to study them individually,” Petersen said.
“But when you look at what is going wrong at a cellular level, they have a lot in common.”
The research team — the first to track all four allergies at once — followed more than a thousand Canadian children from birth to age 5 — about half of whom were diagnosed with one of the four allergies.
The researchers found that each condition correlated with a characteristic bacterial footprint that signified both a compromised gut lining — and heightened inflammation in the gut.
That indicates a breakdown in the rich ecosystem of bacteria, fungi and archaea in the intestine, lead author Courtney Hoskinson of UBC said.
“Typically, our bodies tolerate the millions of bacteria living in our guts because they do so many good things for our health.”
But researchers found that — as in so many relationships — good boundaries were necessary to keep things healthy.
In particular, Hopkinson said, “some of the ways we tolerate [the microbial community] are by keeping a strong barrier between them and our immune cells and by limiting inflammatory signals that would call those immune cells into action.”
The breakdown in those barriers led to a spiking immune response, which in turn led to inflammation — all of which correlated with the development of allergies, she added.
The scientists offered some possible methods to decrease risk — although these should be taken as population-level predictions rather than individual medical advice.
For example, Turvey said, “antibiotic usage in the first year of life are more likely to result in later allergic disorders, while breastfeeding for the first six months is protective.”
“This was universal to all the allergic disorders we studied,” he added.