Urban home microbiome shifted toward forest-like bacterial profiles through simple soil-based entryway intervention

University of Eastern Finland study shows that adding forest soil to rugs increases healthy bacterial diversity in urban homes, potentially lowering asthma risks.

By: AXL Media

Published: Mar 31, 2026, 11:28 AM EDT

Source: Information for this report was sourced from University of Eastern Finland

Reengineering the Indoor Microbial Environment

A new collaborative study has confirmed that the microbial composition of urban residences can be significantly altered through the intentional introduction of environmental microbiota. By applying forest soil to entryway doormats, researchers successfully shifted the indoor microbiome of Finnish homes to more closely resemble the diverse bacterial profiles found in natural outdoor settings. This intervention addresses the "hygiene hypothesis," which suggests that the lack of exposure to diverse environmental microbes in sterile urban environments contributes to the rising prevalence of inflammatory conditions.

Targeting Respiratory Exposure at Infant Heights

The research team found that the impact of the soil intervention was most significant in the zones where it matters most for childhood development. According to lead author Martin Täubel, the application of forest soil to a rug led to a measurable rise in soil-associated bacteria in the indoor air, with the effect being most pronounced at infant breathing height. These findings are particularly relevant because early childhood is a critical window for the activation of immunoregulatory pathways, and the home environment serves as the primary source of microbial exposure during this period.

Measuring the Shift in Bacterial Diversity

To track the effectiveness of the microbial transfer, scientists analyzed house dust samples using DNA sequencing and quantitative PCR (qPCR) over several weeks. The results showed a significant increase in the Farm-home Resembling Microbiota Index (FaRMI), a specific microbial signature previously linked to a lower risk of developing asthma. While environmental bacterial diversity increased, the relative proportion of human-associated bacteria—which often dominate urban indoor spaces—showed a corresponding decrease, suggesting a more balanced and natural indoor ecosystem.