Hygiene Hypothesis Research Articles

The Effect of Lacticaseibacillus rhamnosus, Lacticaseibacillus paracasei, and Bifidobacterium animalis ssp. lactis on the Prevention of Asthma in an Animal Model.

The increase in the prevalence of asthma, particularly in urban communities, has encouraged investigations into preventive strategies. The hygiene theory proposes that early exposure to infections and unhygienic conditions during childhood influences immune system development, potentially protecting against allergic diseases. The mechanisms involved are related to alterations in the intestinal microbiota, such as with probiotics. This study aimed to evaluate the preventive effect of Lacticaseibacillus rhamnosus, Lacticaseibacillus paracasei, and Bifidobacterium animalis ssp. lactis, administered isolated or in combination, at various concentrations, on asthma in an animal model. Mice received two concentrations (1 × 109 and 1 × 1010CFU/ml) of three probiotics, isolated and in combination, over 26 consecutive days, initiating 10days before sensitizing and challenging with ovalbumin. In vivobronchial hyperresponsiveness and airway and lung inflammation were assessed. The administration of L. paracasei, L. rhamnosus, and B. animalis spp. lactis in different concentrations, isolated or in combination, did not reduce hyperresponsiveness and airway and lung inflammation. As probiotic effects are strain and dose-dependents, specific studies are necessary to assess the effect of different probiotic strains, doses, and regimes.

Immuno-therapeutic and prophylactic potential of Trichinella spiralis antigens for inflammatory bowel diseases

Ulcerative colitis (UC), a severe chronic inflammatory disorder of the colon, is one of the inflammatory bowel diseases (IBD) that affects humans and several domestic animal species, including cats and dogs. Helminth infections and autoimmune diseases are inversely correlated, as explained by the hygiene hypothesis, which suggests that IBD is infrequent in countries where helminth infections are common but more prevalent in developed nations. This study investigated the therapeutic and prophylactic potential of Trichinella spiralis (T. spiralis) antigens in an experimental colitis model for IBD. Mice were divided into eight groups: normal model, colitis model, larval antigen prophylaxis, adult antigen prophylaxis, larval antigen therapeutic, adult antigen therapeutic, larval antigen prophylaxis and therapeutic, and adult antigen prophylaxis and therapeutic. Colitis was induced intrarectally by administering a single dose of 0.2 ml of acetic acid, except in the healthy group, which received PBS (0.2 ml). The mice were euthanized 12 days after colitis induction. The therapeutic and prophylactic potential of T. spiralis antigens were assessed through colitis severity and histopathological, immunological, and immunohistochemical examinations. The results showed a significant reduction in Disease Activity Index (DAI), an increase in goblet cells' acidic mucin levels, reduced iNOS and TNF-α expression, and decreased serum levels of IFN-γ and IL-10 cytokines in Groups IV-VIII compared to the colitis model, particularly in the group that received adult worm antigen both prophylactically and therapeutically. This study demonstrated that T. spiralis antigens, especially from adult worms, had protective and therapeutic effects on experimental colitis, with a superior effect when administered both before and after colitis induction by reducing inflammation and modulating the immune response. Thus, T. spiralis antigens may improve disease outcomes and provide a novel treatment approach for ulcerative colitis.

Why are healthcare professionals leaving NHS roles? A secondary analysis of routinely collected data

BackgroundMuch policy attention focuses on increasing the supply of workers in the English NHS but there has been less attention paid to the rise in leavers. This paper seeks to explore how existing data sets can illuminate the decision-making of leavers and inform actions that could mitigate this.MethodSecondary analysis of routinely collected data from 79 workforce projects in the UK (n = 46 339 participants) over a 4-year (2019–2023) period was undertaken. Free text data we extracted and analysed using content analysis, sentiment analysis and text mining. Inclusion criteria were those who stated they had resigned, had confirmed retirement date, and had secured employment elsewhere either within or without the sector but had not yet resigned. Exclusion criteria were those who had not indicated they were leaving or indicated intention to leave. These findings were then compared with themes from Herzberg’s work hygiene theory and Hoffat and Woods’s professional practice environment theory.ResultsMultiple reasons were given for leaving. Findings were congruent with Herzberg’s two factor work hygiene theory and demonstrate that leavers are driven by the inability to meet their intrinsic motivation to practice according to their professional standards as much as by terms and conditions. Leavers describe suboptimal professional practice environments which produce obstacles to achieving their work objectives and leaving their intrinsic motivation frustrated.ConclusionWhilst reasons for leaving differ between people, there is a relationship between intrinsic motivation (why they want to do the job) and the conditions in which they try to do the job. This study suggests that looking beyond the primary reason for leaving given in the national dataset could identify how the practice environment influences the decision.

Schistosoma excretory/secretory products: an untapped library of tolerogenic immunotherapeutics against food allergy.

Food allergy (FA) is considered the 'second wave' of the allergy epidemic in developed countries after asthma and allergic rhinitis with a steadily growing burden of 40%. The absence of early childhood pathogen stimulation embodied by the hygiene hypothesis is one explanation, and in particular, the eradication of parasitic helminths could be at play. Infections with parasites Schistosoma spp. have been found to have a negative correlation with allergic diseases. Schistosomes induce regulatory responses to evade immune detection and ensure their long-term survival. This is achieved via excretory/secretory (E/S) products, consisting of proteins, lipids, metabolites, nucleic acids and extracellular vesicles, representing an untapped therapeutic avenue for the treatment of FA without the unpleasant side-effects and risks associated with live infection. Schistosome-derived immunotherapeutic development is in its infancy and novel discoveries are heavily technology dependent; thus, it is essential to better understand how newly identified molecules interact with host immune systems to ensure safety and successful translation. This review will outline the identified Schistosoma-derived E/S products at all life cycle stages and discuss known mechanisms of action and their ability to suppress FA.

Social hygiene in Germany in the early twentieth century: Science subject and methodology

Introduction. At the beginning of the 20th century, the theory of social hygiene was widely recognized worldwide. This science’s birthplace is Germany, and its founder is Alfred Grotjahn. In 1904, he presented a scientific concept of social hygiene, including a new hygienic science, field of study, subject, methodology, and scientific methods. Purpose. This study examines the scientific approaches to social hygiene in German academic literature from the early 1900s to the late 1920s. Materials and methods. This study gathered the necessary data by comprehensively reviewing key German manuals and periodic annual compilations. Results. A. Grotjahn viewed social hygiene as a science combining descriptive and normative approaches. By social hygiene, he meant the study of conditions affecting the social hygiene culture of individuals about place, time, and social environment, as well as their offspring. The descriptive component of the science aims to analyze these conditions, while the normative side investigates measures to improve hygienic culture among individuals and their offspring. He proposed to apply the probability theory as a scientific methodology and utilized the scientific methods of statistics, economics, history, sociology, and politics. Until the 1920s, German social hygienists followed Grotjahn’s theory in their manuals. In the mid-1920s, Ferdinand Huppe introduced the concept of constitutional hygiene theory in a multi-volume handbook of social hygiene. It was based on the methods of biology and the principles of racial hygiene. Conclusion. Grotjahn’s scientific concept of social hygiene underwent significant changes and evolution in the early twentieth century. These transformations, which were influenced by introducing new theories and applying different scientific methods, are crucial to understanding the development of social hygiene as a discipline.

Toward a Theory of Motivation and Performance for Organizational Employees: A Case Study of a Walmart Store in the USA

Hygiene Theory, and so forth. The literature review covers both theory developments and empirical evidence. The study surveyed 135 Walmart employees and interviewed 23 Walmart employees. Based on this empirical study, the authors proposed motivation and performance theories for organizational employees. For employee motivation theory, seven factors are identified to contributing to employee motivation: 1) Compensation and benefits; 2) Training and development opportunities; 3) Supportive work environment; 4) Recognition and appreciation; 5) Clear communication and feedback; 6) Career growth opportunities; and 7) Support for work-life balance. For employee performance theory, six factors are identified to leading to employee performance: 1) Opportunities for professional development; 2) Competitive compensation and benefits; 3) A positive work culture; 4) Regular feedback and recognition; 5) Collaboration and teamwork; and 6) Employee well-being. The study also challenges Herzberg’s Two Factor Theory. Instead of differentiating “hygienic factors” and “motivator factors”, the authors conclude that the boundary of “hygienic factors and motivator factors” is blurred, and instead they should be put in a comprehensive package of motivation basket.

Prevalence of Helminth Infections in Patients with Celiac Disease

Introduction: The aim of this study was to investigate the association between helminth infections and celiac disease (CeD), examining various demographic and clinical factors in CeD cases compared to controls. Methods: We conducted a retrospective case-control study utilizing Leumit Health Care Services’ electronic health records. The study encompassed individuals with CeD and a matched control group. We analyzed demographic and clinical characteristics, examining their association with helminth infections. Results: We observed CeD cases and controls had similar mean ages (17.8 years vs. 18.0 years, p = 0.565) and gender distributions (64.0% females in both groups, p = 0.999). There were no significant differences in socioeconomic status and ethnic distribution between the two groups. Most of the helminthiases in the CeD group were due to intestinal helminthiases, and most of the intestinal helminthiases were nematode (roundworm) infections. Enterobiasis (the pinworm Enterobius vermicularis) is involved in most cases (odds ratio 1.32, 95% confidence interval 1.20–1.45, p < 0.001). While the prevalence of ascariasis and anisakiasis was also higher in the CeD group, these differences were not statistically significant (p = 0.115 and p = 0.174, respectively). No significant differences were found in the prevalence of other specific helminth infections, such as echinococcosis, cestode infections, and strongyloidiasis. Conclusions: This study reveals an unexpected association between CeD and helminth infections, challenging prevailing hypotheses, particularly within the context of the hygiene hypothesis. These findings warrant further investigation to elucidate the mechanisms underlying this intriguing relationship.

Geohelminths: Use in the Treatment of Selected Human Diseases.

Research on the therapeutic use of parasites has been ongoing since the development of the "hygiene hypothesis". Parasites can stimulate the Th2-dependent response and suppress the Th1-dependent response, which is intensified in many diseases, especially allergic and autoinflammatory ones. In this review, we present the types of parasites used in helminth therapy and the range of diseases in which they may be useful. We also present the results of clinical trials conducted so far, which confirm the safety of such therapy and provide promising outcomes.

The Pathogenesis of Type 1 Diabetes.

Type 1 diabetes (T1D) is a chronic autoimmune disease with a metabolic outcome. Studies over the past decades, have identified the contributions of genetics, environmental factors, and disorders of innate and adaptive immunity that collectively cause β-cell killing. The risk for T1D can be genetically identified but genotypes alone do not identify factors that lead to disease progression. The incidence of T1D has been increasing in the past few decades, which may be due to reduced exposure to infections and other environmental factors that can reduce autoimmunity (hygiene hypothesis). Once initiated, the disease pathogenesis progresses through stages that have been defined on the bases of immunologic (i.e., autoantibodies) and metabolic markers (glucose tolerance). The stages only loosely capture the risk for the time to diagnosis of disease, do not directly reflect disease activity, and there may be variance in the rate of progression within stages. In a general way, the stages can be used to identify patients at risk in whom interventions may be considered to modulate progression. This was achieved with the approval of teplizumab, a humanized anti-CD3 monoclonal antibody, for delaying the diagnosis of T1D.

Inhibition of TLR4 and NLRP3 leads to the exacerbation of IgE specific antibodies in mouse allergic models based on subcutaneous or intranasal immunization respectively

A significant increase in the prevalence of diseases linked with IgE production can be seen in recent years, but the question about the role of TLR receptors in this process remains controversial. According to the hygiene hypothesis, the decrease of the contact of the individual with pathogens that contain PRR receptor ligands in the recent years leads to the development of allergic diseases. The aim of this work was to investigate whether TLR4 and NLRP3 receptor activation contributes to allergen-specific antibody formation. BALB/c mice were immunized according to two different protocols. In the first one, OVA antigen was administered in 0.1 µg dose 2-3 times a week for 6 weeks by subcutaneous route. In the second one, OVA was administered in 0.3 µg dose intranasally in combination with 4 ng of benzo(a)pyrene (BaP) 2 times a week for 8 weeks. In both cases, TLR4 and NLRP3 receptor inhibitors, namely TLR4-IN-C34 in 1 mg/kg dose and CY- 09 in 20 mg/kg dose respectively were also administered to the some of the mice. Specific antibody production was determined by ELISA. Immunization of mice with TLR4-IN-C34 significantly (p 0.01) amplify IgE production (about 2.5 times in comparison with control group), but has no effect on specific IgG1 production in subcutaneous model. Specific IgE titers in the control group immunized without small molecule inhibitor and in the TLR4-IN-C34 group were (3±0.6) × 103 and (8±2) × 103, respectively. In this model, CY-09 administration has no effect on humoral immune response. In the secondary (intranasal) model, BaP significantly increase specific IgE and IgG1 production. CY-09 but not TLR4-IN-C34 administered in combination with BaP significant (p 0.05) and approximately 2 times enhances specific IgE but not IgG1 production. Specific IgE titers in the control group without inhibitor and in the CY-09 group were (2.0±0.4) × 102 and (5.1±0.3) × 102, respectively. So, PRR-activation, in our case activation of TLR4 in the model based on subcutaneous immunization or NLRP3 in the model based on intranasal antigen administration with BaP suppressed the production of allergen-specific IgE, but not IgG1. These data are in consistent with the hygiene theory of allergy development.

Contacts with environmental biodiversity affect human health: links revealed during the initial waves of the COVID-19 pandemic

The gradual decrease in the prevalence of serious infectious diseases over the last century has been followed by increase in so called “modern” diseases, including allergies, chronic inflammatory conditions, psychiatric, and metabolic disorders. Between 2019 and 2022, public awareness of the threat of infectious diseases in humans was renewed by the global pandemic of a new type of a coronavirus, the SARS-COV-2. This public interest opened improved possibilities to test hypotheses on the factors associated with inter-individual variation in susceptibility to infectious and “modern” diseases. Based on the Hygiene hypothesis and Biodiversity hypothesis, we predicted that contacts with natural environment and wildlife in childhood and/or in adulthood can improve general health and decrease the risks of severe COVID-19 progression or prevalence of the “modern” diseases, namely the allergies. Here we report the results of an online, self-evaluating questionnaire survey conducted in the Czech Republic, where we contrasted selected health issues, and linked them to the living environment, including the level of contacts with biodiversity. In a sample of 1188 respondents, we revealed a significant association of time spent in nature or contacts with biodiversity with physical and mental health, or incidence of allergies. This is unlike the COVID-19 progression, which was related to age, physical health, smoking, allergies, and interaction of age with smoking, but not to contacts with the natural environmental diversity. Our findings regarding to physical and mental health and allergies are in agreement with the Biodiversity hypothesis of allergy and, linking human and environmental health, they urge for One Health approach application.

Revisiting The Hygiene Theory; Hepatitis A And Tuberculosis Versus Atopy

Objectives: According to the hygiene hypothesis an inverse association between allergic sensitization and exposure to infections and has been reported. In this study, we investigated the relationship between atopy and TB and hepatitis A virus (HAV) infections in children. Methods: A cross-sectional study was performed and included 39 healthy children who were followed up with TB, 40 healthy children who were with HAV seropositive, and 30 healthy children who were seronegative for HAV and tuberculin skin test (TST) response as negative. Serological tests for HAV (anti-HAV immunoglobulin G), skin prick test (SPT) investigations for the detection of atopy, and TST were carried out. Results: The study included 39 (16 males, 23 females) with TB, 40 (16 males, 24 females) with HAV seropositive, and 30 (10 males, 20 females) healthy controls. There was no statistically significant difference between the groups in terms of age and gender (p&gt;0.05). The SPT positivity was 28.2% (n=11) in the TB group, 15% (n=6) in the HAV group, and 30% (n=9) in the control group. There was no statistically significant difference between the groups in terms of SPT positivity (p=0.148). There was no statistically significant difference between the groups in terms of total serum IgE level (p=0.776). Conclusions: Our study does not support the hypothesis that HAV and TB suppress the development of atopy. We think that encountering infections during the immune maturation period is a condition that is protective in the development of atopy due to multifactorial reasons.

Structural Insights on Cross-Reactivity of Mite Allergens with Helminth Proteins

Updated notions about the so-called hygiene hypothesis consider now that helminths may have influence in the training of the immune system during childhood. Considering the similar type of immune response between helminth infections and allergic illnesses, the objective of this study was to evaluate how structural and functional conservation between house-dust mite allergens and their helminth orthologs might contribute to the cross-induction of IgE responses in allergies and helminthiasis. Amino acid sequences from group-1, -2, -5, -9, -10, -18, -21, and -23 allergens of the house dust mite Dermatophagoides pteronyssinus were retrieved from curated databases, and orthologs were identified in other mite species and different helminth parasites. We also assessed structural, conservational, functional, and immunologic relationships between these major mite allergens and their helminth counterparts. De novo 3D-modelling, B-cell epitopes prediction, structural conservation, and docking analyses were analyzed by Robetta platform, ElliPro and CBTope, RaptorX, and Z-Dock, respectively. Our results extend previous findings on structural conservations between major allergens and parasite proteins and show that these conservations go beyond the well-known conservations and may account for the observed immunological cross-reactions. This understanding can contribute in the near future to the development of more specific serological testing for mite-induced allergies and helminthiasis.

Evaluating the Toxocara cati extract as a therapeutic agent for allergic airway inflammation.

The hygiene hypothesis suggests that early life exposure to helminth infections can reduce hypersensitivity in the immune system. The present study aims to evaluate the effects of Toxocara cati(T. cati) somatic products on allergic airway inflammation. Between 2018 and 2020, T. cati adult worms were collected from stray cats in Mashhad, Iran (31 out of 186 cats), and their somatic extract was collected. Thirty BALB/cmice were equally divided into three groups, including the OVA group (sensitized and challenged with ovalbumin), the somatic administered group (received somatic extract along with ovalbumin sensitization), and the PBS group (sensitized and challenged with phosphate buffer saline). Bronchoalveolar lavage(BAL)fluid was collected to assess the number of cells, and lung homogenates were prepared for cytokine analysis. Histopathological analysis of the lungs was performed, and inflammatory cells and mucus were detected. Cytokine levels (IL-4, IL-5, IL-10) were measured using enzyme-linked immunosorbent assay (ELISA), and ovalbumin-specific immunoglobulin E (IgE) levels were determined using a capture ELISA. The somatic group significantly decreased regarding the lung pathological changes, including peribronchiolitis, perivasculitis, and eosinophil influx, compared to the group treated with ovalbumin alone. These changes were accompanied by a decrease in proinflammatory cytokines IL-4 and IL-5 and an increase in the anti-inflammatory cytokine IL-10, indicating a shift towarda more balanced immune response. The number of inflammatory cells in the BAL fluid was also significantly reduced in the somatic group, indicating a decrease in inflammation. These preclinical findings suggest that in experimental models, T. cati somatic extract exhibits promising potential as a therapeutic agent for mitigating allergic airway inflammation. Its observed effects on immune response modulation and reduction of inflammatory cell infiltration warrant further investigation in clinical studies to assess its efficacy and safety in human patients.

Predicting COVID-19 Cases and Deaths Utilizing Hygiene Hypothesis Surrogate Factors: A Global Analysis

Predicting COVID-19 Cases and Deaths Utilizing Hygiene Hypothesis Surrogate Factors: A Global Analysis

Immune experiences alter tolerance in T cell-mediated autoimmunity.

Abstract Autoimmune diseases afflict &amp;gt;20M Americans and alarmingly the incidence of autoimmune diseases is increasing particularly in children. The hygiene hypothesis (HH) proposes that there is an inverse correlation between microbial exposure and subsequent development of autoimmunity, i.e., the “cleaner” the environment, the higher the probability that autoimmunity develops. Critically, how microbial exposures and infections alter self-antigen (Ag), a critical component of immune tolerance, is unknown. Our data show that immune-experienced mice have decreased self-specific CD8 T cell priming and organ pathology mediated by resident cells in lymph nodes (LN). Resident Ag-bearing LN stromal cells isolated from immune-experienced mice induced less self-specific CD8 T cell proliferation in vitro indicating changes in self-Ag. The HH determines that environmental stressors are important drivers of autoimmunity, yet the human immune experience is poorly modeled in SPF models of tolerance and autoimmunity. Therefore, we used mice exposed to natural mouse pathogens, "dirty" mice showed a decrease in T cell activity to self-Ag. The cohousing of NOD mice with pet shop mice resulted in zero mice developing autoimmune diabetes. Overall, our data suggest novel mechanisms by which self-antigen is altered in lymph nodes due to previous immune experiences addressing a critical mechanism behind the hygiene hypothesis, intersecting TCR reactivity with environmental impact.

Helicobacter pylori Infection Does Not Protect Against Allergic Diseases: Evidence From a Pediatric Cohort From Northern Sardinia, Italy

ABSTRACTBackgroundThe “hygiene hypothesis” states that reduced exposure to microbial antigens due to an excessively hygienic environment can increase the risk of developing autoimmune diseases, including atopic disorders and asthma. In recent decades, there has been a progressive decline in the prevalence of numerous microorganisms following improved hygienic‐sanitary conditions. More specifically, several studies reported an inverse association between the reduction in Helicobacter pylori infection and the rise of asthma and allergic disorders.AimTo evaluate the prevalence of atopic disorders in a pediatric population in relation to seropositivity against H. pylori.MethodsChildren from Northern Sardinia, Italy, referred to the local Children's Hospital for any reason, were investigated to identify risk factors, especially H. pylori infection, associated with atopic disorders. A validated questionnaire, including demographics, house size, history of breastfeeding, residence, school or daycare center attendance, exposure to animals, and a defined diagnosis of atopy—including asthma—was filled out by a trained pediatrician according to parents' answers and child records. A blood sample was collected from each participant and immunoglobulin G against H. pylori was assessed by a locally validated ELISA test.ResultsThe seroprevalence of H. pylori infection was 11.7% among 492 children (240 females). Thirty‐two children had a confirmed diagnosis of asthma and 12 of allergy. No one child showed both conditions. Statistically significant differences in H. pylori seropositivity were not detected between children with or without atopy (8.4% vs. 12.6; p = 0.233). Although atopic disorders were more frequent in children exposed to traditional atopic risk factors, none of them showed to be significant after adjusting for all covariates.ConclusionsSerologically assessed H. pylori infection was not significantly associated with a reduced risk of atopic diseases in children.

Lactate Dehydrogenase-Elevating Virus Infection Inhibits MOG Peptide Presentation by CD11b+CD11c+ Dendritic Cells in a Mouse Model of Multiple Sclerosis.

Infections may affect the course of autoimmune inflammatory diseases of the central nervous system (CNS), such as multiple sclerosis (MS). Infections with lactate dehydrogenase-elevating virus (LDV) protected mice from developing experimental autoimmune encephalomyelitis (EAE), a mouse counterpart of MS. Uninfected C57BL/6 mice immunized with the myelin oligodendrocyte glycoprotein peptide (MOG35-55) experienced paralysis and lost weight at a greater rate than mice who had previously been infected with LDV. LDV infection decreased the presentation of the MOG peptide by CD11b+CD11c+ dendritic cells (DC) to pathogenic T lymphocytes. When comparing non-infected mice to infected mice, the histopathological examination of the CNS showed more areas of demyelination and CD45+ and CD3+, but not Iba1+ cell infiltration. These results suggest that the protective effect of LDV infection against EAE development is mediated by a suppression of myelin antigen presentation by a specific DC subset to autoreactive T lymphocytes. Such a mechanism might contribute to the general suppressive effect of infections on autoimmune diseases known as the hygiene hypothesis.

Hygiene and Sanitation Implementation in Kitchen Aston Jember Hotel &amp; Conference Center

The research on the implementation of hygiene and sanitation in the kitchen of the Aston Jember Hotel &amp; Conference Center is presented in this report. In order to make high-quality cuisine, the author of this scientific paper wishes to know what measures are used to preserve kitchen hygiene and sanitation at the Lekker Restaurant Hotel Aston Jember. The author employs a qualitative descriptive research approach to accomplish this goal, which involves performing observations, interviews, and the use of documentation materials. Additionally, the theory of kitchen hygiene and sanitation is combined with other aspects connected to enhancing the quality of these things. The people with power over matters of sanitation and kitchen hygiene were identified as informants for this study. Data from informants, in the form of written or spoken material, was carefully read again, analyzed, and described.

Urban indoor gardening enhances immune regulation and diversifies skin microbiota — A placebo-controlled double-blinded intervention study

According to the hygiene and biodiversity hypotheses, frequent exposure to environmental microbiota, especially through soil contact, diversifies commensal microbiota, enhances immune modulation, and ultimately lowers the risk of immune-mediated diseases. Here we test the underlying assumption of the hygiene and biodiversity hypotheses by instructing volunteers to grow edible plants indoors during the winter season when natural exposure to environmental microbiota is low. The one-month randomized, placebo-controlled double-blind trial consisted of two treatments: participants received either microbially diverse growing medium or visually similar but microbially poor growing medium. Skin microbiota and a panel of seven immune markers were analyzed in the beginning of the trial and after one month. The diversity of five bacterial phyla (Bacteroidetes, Planctomycetes, Proteobacteria, Cyanobacteria, and Verrucomicrobia) and one class (Bacteroidia) increased on the skin of participants in the intervention group while no changes were observed in the placebo group. The number of nodes and edges in the co-occurrence networks of the skin bacteria increased on average three times more in the intervention group than in the placebo group. The plasma levels of the immunomodulatory cytokine interleukin 10 (IL-10) increased in the intervention group when compared with the placebo group. A similar trend was observed in the interleukin 17A (IL-17A) levels and in the IL-10:IL-17A ratios. Participants in both groups reported high satisfaction and adherence to the trial. The current study provides evidence in support of the core assumption of the hygiene and biodiversity hypotheses of immune-mediated diseases. Indoor urban gardening offers a meaningful and convenient approach for increasing year-round exposure to environmental microbiota, paving the way for other prophylactic practices that might help prevent immune-mediated diseases.