# Research timeline and gaps: Hygiene Hypothesis

Selected publication milestones, not an exhaustive history or discovery priority claim.

**2001 — A defined perinatal probiotic regimen tests eczema prevention.** [Original PMID11297958](https://pubmed.ncbi.nlm.nih.gov/11297958/).

**2008 — Microbiota and host genotype interact in experimental autoimmune diabetes.** [Original PMID18806780](https://pubmed.ncbi.nlm.nih.gov/18806780/).

**2012 — Neonatal versus adult colonization distinguishes an immune-development window in mice.** [Original PMID22442383](https://pubmed.ncbi.nlm.nih.gov/22442383/).

**2015 — Early microbial taxa link human risk observations with recipient-mouse airway experiments.** [Original PMID26424567](https://pubmed.ncbi.nlm.nih.gov/26424567/).

**2016 — Amish–Hutterite observations combine with contrasting dust perturbations in mice.** [Original PMID27518660](https://pubmed.ncbi.nlm.nih.gov/27518660/).

**2016 — Different bacterial LPS signals link human cohorts with NOD-mouse experiments.** [Original PMID27133167](https://pubmed.ncbi.nlm.nih.gov/27133167/).

**2022 — Daycare biodiversity intervention tests immune and microbiome markers.** [Original PMID35930838](https://pubmed.ncbi.nlm.nih.gov/35930838/).

**2026 — ORBEX reports a null clinical primary outcome after bacterial-lysate treatment.** [Original PMID42705251](https://pubmed.ncbi.nlm.nih.gov/42705251/).

## Research gaps

Microbial quality, amount, route and timing are distinct exposures, not one hygiene variable.

Human autoimmune clinical prevention remains a separate missing causal branch.

Positive eczema effects do not consistently extend to sensitization, food allergy or asthma.

Clinical effects may occur without durable microbial engraftment or diversity change; the mediator needs identification.

Environmental soil interventions need disease-incidence follow-up beyond immune biomarkers.

Shared cohort/trial reports and post-hoc genotype/delivery subgroups require prospective independent validation.

## Boundary experiment

Register microbial-factor/consortium restoration in an objectively baseline-defined infant population, with credible placebo, measured exposure/engagement and immune mediation. Prespecify clinical eczema, asthma and separately powered autoimmune endpoints, retain all randomized participants, and independently replicate dose/window and host-genotype predictions. Include antigen/diet/barrier and infection-indication controls.