We spend a lot of time keeping our hands and skin "clean," but a microbiology study suggests a bit of dirt might actually be doing your skin a favour.
What they did
Researchers from the University of Helsinki and University of Tampere wanted to test something called the "hygiene hypothesis," the idea that modern life is too clean, and that less contact with nature and its microbes might be behind the rise in immune-related conditions like allergies, eczema, and asthma.
To test it, they had volunteers rub their hands with 16 different soil and plant materials, and also exposed their skin to small fabric packets filled with moss. Then they swabbed everyone's skin before and after and used gene sequencing to see what had changed in the mix of bacteria living there.
What they found
Just a few minutes of contact with soil and plants was enough to noticeably shift the skin's bacterial makeup. The variety of bacteria on the skin went up, including several major bacterial groups linked to environmental and immune health. In short: touching dirt and plants gave people's skin a quick, temporary boost in microbial diversity.
Why that matters
A more diverse mix of bacteria on the skin is generally considered a good thing. Many scientists believe that early and regular exposure to a wide range of harmless microbes helps "train" the immune system, and that a lack of this exposure in overly sanitised modern environments may be contributing to rising rates of allergies and immune disorders.
The researchers suggest that instead of using single "good bacteria" supplements (e.g. probiotics) or treatments, exposure to naturally diverse materials, like soil, plants, and moss, might do a better job of diversifying the skin's microbial community, precisely because nature isn't limited to just one or two species.
Study limitations
This was a small, short-term study, it only looked at what happens right after contact, not whether the changes last or whether they actually improve health outcomes. The authors themselves say the next step is figuring out whether these changes stick around long-term, and whether they translate into real benefits for the immune system.
The takeaway
You don't need to scrub away every trace of the outdoors. A little contact with soil, plants, or greenery might genuinely be good for your skin's bacterial balance, though the science on how much, how often, and for how long the benefits last is still catching up. It could be as simple as getting into your garden or planting some indoor pot plants, getting out onto nature trails, making a terrarium, and finding local urban farms where you can pick your own food straight from the soil to enjoy the many positive effects to emotional and physical wellbeing.
Source: Grönroos M, Parajuli A, Laitinen OH, Roslund MI, Vari HK, Hyöty H, Puhakka R, Sinkkonen A. "Short-term direct contact with soil and plant materials leads to an immediate increase in diversity of skin microbiota." MicrobiologyOpen. 2019;8(3):e00645. doi: 10.1002/mbo3.645. pmc.ncbi.nlm.nih.gov/articles/PMC6436432
