Introducing forest soil on an entryway doormat shifted the indoor microbiome of Finnish homes closer to bacterial profiles found outdoors, with less contribution from human-associated bacteria, a new study shows. In the future, such interventions rebalancing the home microbiome could be used for health promotion, especially in urban settings. The study was led by the Finnish Institute for Health and Welfare and the University of Eastern Finland and is published in the journal Microbiome.

"Applying forest soil onto a rug led to a clear rise in forest soil-associated bacteria in the air. The effect was most pronounced at infant breathing height for the first two weeks after application, and the signal was also detectable in other areas of the home," says lead author, chief researcher Martin Taubel.

Childhood home microbiome may influence long-term health

Because early childhood is spent largely indoors, the home microbiome is a major source of microbial exposures that activate children's immunoregulatory pathways and may influence their long-term health. Reduced encounters with environmental microbes have been observed in urban homes and are linked to an increased risk of inflammatory diseases, including asthma and allergies. This has sparked interest in interventions to modify indoor microbial exposures toward health-promoting interactions.

. . .