Throughout human evolution, humans have coexisted with a diverse array of microorganisms, including the resident microbiome of the skin and gut as well as transient microbes from the environment. These microorganisms play a central role in the development and regulation of the immune system. The Biodiversity Hypothesis proposes that exposure to natural environments enriches the human microbiome, supports immune balance, and protects against allergies and inflammatory diseases. However, urbanization and modern lifestyles have weakened this interaction, limiting exposure to environmental microbes drastically. This has negative consequences to our immune system and can lead to increased incidences of several immune-system disorders.
Despite increasing urbanization and the health risks associated with reduced contact with natural environments, these effects may be mitigated by reintroducing biodiversity. Intervention studies using exposure to soil enriched with microbial diversity have shown beneficial immunological outcomes. In a Finnish daycare study, 28 days of exposure to biodiversity-enriched soil increased the diversity of skin and gut microbiota, elevated regulatory T cell (Treg) frequency, and shifted cytokine profiles toward a less inflammatory state.
These findings suggest that enhancing exposure to natural environments and restoring regular contact with microbial biodiversity can yield immunological benefits. This underscores the importance of re-establishing daily interactions with nature, particularly in highly urbanized settings where such exposure is limited. However, access to biodiverse environments remains constrained for many urban populations. To address this, a Finnish microbial extract has been developed to mimic natural microbial diversity and reintroduce it to our immune system via the skin. This can be used as an active ingredient in cosmetic products, which enables safe, practical, and accessible exposure to microbial diversity, offering a feasible strategy to restore beneficial nature contact in everyday life.
Clinical trial on atopic dermatitis
Atopic dermatitis (AD) is a chronic inflammatory skin disease associated with immune dysregulation and impaired skin barrier function, leading to pruritus, dryness, and eczematous lesions. It is the most common inflammatory skin disorder, affecting up to 20% of children and adolescents globally. The pathogenesis of AD is multifactorial, with urban living environments and genetic predisposition identified as key risk factors. Epidemiological studies indicate that individuals with atopy are exposed to lower environmental biodiversity and exhibit reduced diversity of Gammaproteobacteria on the skin compared with healthy individuals. Additionally, a dose-dependent association has been observed between atopy risk and the microbial composition of house dust.
The clinical trial described here investigates whether enhancing exposure to environmental microbial biodiversity can improve AD outcomes by addressing microbial deprivation. Specifically, the aim was to evaluate whether a skin lotion containing a biodiversity-rich microbial extract affects symptoms and medication use in adults with AD.
The study was randomized, double-blinded, placebo-controlled clinical trial. A total of 142 Finnish volunteers aged 18–67 years, meeting the Hanifin and Rajka diagnostic criteria for AD, were enrolled. Participants were randomized into an intervention group (n=72) and a control group (n=70). Both groups used the same base lotion; however, the lotion for intervention group contained 1% of microbial extract as the active ingredient. This extract comprises over 600 bacterial species, mimicking the microbial diversity of Finnish forest soil and nature contact. The microbial extract is inactivated, and its suitability for atopic and/or sensitive skin has been previously demonstrated in in vivo studies.
Participants applied the assigned lotion to both arms and designated study areas at least three times per week over a period of 5–9 months, covering the Finnish winter season. This timeframe was selected due to the exacerbation of AD symptoms in cold conditions (12, 17). Participants had three clinical visit throughout the trial, they were conducted at baseline, midpoint, and at study completion. Transepidermal water loss (TEWL, by Delfintech Vapometer) and erythema index (Delfintech Skin Color Catch) were measured from standardized sites (eczema area & standard site on forearm) during the clinical visits as well as, the disease severity using the Eczema Area and Severity Index (EASI). Patient-reported outcomes were gathered biweekly via online questionnaires and included the Patient-Oriented Eczema Measure (POEM), Peak Pruritus Numerical Rating Scale (NRS itch), medication use, and adverse events. Other measurements and immunological markers were also taken at the clinical visits. Over the course of the study, 15 participants (10.6%) withdrew, while an additional seven completed questionnaire assessments but did not attend the final clinical visit. A subset of 19 participants (13.7%) chose to avoid all atopy medications except antihistamines; to prevent potential bias, these individuals were excluded from analyses related to medication use.
Microbial extract benefits atopic dermatitis – a novel solution
The medication use of participants was monitored throughout the trial and result show fewer medication users in the intervention group. The difference was especially visible in the beginning of winter. In addition to fewer atopy medication users, there were also less atopy medication days in the intervention group compared to control group. This pattern remained consistent regardless of whether the data were examined over calendar time (chronologically) or relative to the start of the intervention.
Despite the difference in AD medication use between the groups, there were no difference in eczema severity measured with Eczema Area Severity Index (EASI), nor Patient oriented eczema measure (POEM). This supports the idea that experimental group managed with less medication even though the eczema severity was similar with the control group.
Regular use of the microbial extract also benefited atopic skin by preventing winter-related deterioration of the skin barrier. Transepidermal water loss (TEWL) increased significantly at the standard measurement site in the control group, whereas no such change was observed in the intervention group. Similarly, the erythema index increased at the designated eczema site in the control group at the midpoint assessment, while no statistically significant change was detected in the intervention group.
This clinical trial on atopic individuals demonstrates that regular exposure to inactivated natural microbial diversity can alleviate symptoms of atopic dermatitis, which is a promising new approach to supplement the current AD treatments from a new perspective. The new microbial solution to restore the lost connection to nature’s microbial diversity reduced the need for atopy medications and improved clinical indicators such as skin barrier function and inflammation providing an innovative and new solution for AD patients.
This clinical trial in individuals with atopic dermatitis demonstrates that regular exposure to inactivated natural microbial diversity can help alleviate AD symptoms, offering a promising complementary approach to current treatments. By restoring contact with nature’s microbial diversity, the intervention lotion reduced the need for atopy medications and improved clinical outcomes, including skin barrier function and redness, providing an innovative and novel solution to complement current AD skincare.
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