GROWING up on a farm, with early years exposure to a wide variety of mucky dust, could significantly lower as child's risk of developing asthma, a new scientific study has suggested.

Researchers at Finland's National Institute for Health and Welfare analysed the microbes in living room floor dust from the homes of a group of 197 children living in rural areas of Finland – half living on farms – and 182 children living in suburban or urban places. The team took their samples when the children were two-months-old and likely to be crawling, and more exposed to microbes on the floor, and then followed up their research at six-years-old to see how many of the children were diagnosed with asthma.

In the rural group, there was a clear difference in the dust found in farm homes, with a much higher variety of bacteria, including some from livestock, that were not present in homes of non-farming families. In turn, the children raised in these homes had more than half the rate of asthma of their urban counterparts.

Non-farm homes were shown to have a higher proportion of human-associated bacteria, including members of the Streptococcaceae family and Straphylococcus genus. About 19% of the children on these non-farm homes had asthma, while only 9% of kids raised on farms had the same problem.

On their publication in the New Scientist, lead researcher Pirkka Kirjavainen said of the findings: “Where there are more outdoor microbes and a low abundance of human microbes, we see lower asthma rates.

“There is an indication that early life exposure matters the most. Later exposure would seem to have an influence on asthma, but this is the optimal window to measure,” said Kirjavainen.

For the suburban children, the researchers found that the homes with a microbial community that was, for whatever reason, more like that of farm homes were correlated with a lower risk of asthma in their resident children at age six.

When the team studied blood samples from the children, they found that those in homes with more farm-like bacteria didn’t produce immune responses to the bacteria, so they tolerated them better. The team then replicated this study with a group of 1031 German children, and found the same relationship between farm-like microbes in non-farm homes and a reduced risk of childhood asthma.

Kirjavainen noted that there was a small association between having pets and farm-like microbes in the home, which could be due to the animals bringing in soil particles. The team saw no effect when they took into account gender, parental allergies, maternal education, smoking during pregnancy, or the number of siblings a child had.

The next step in the Finnish research is to determine what it is about the microbes that make them beneficial, and potentially devise a therapy that could induce these immune system effects in children.