The in vivo study remains the gold standard for evaluating the effect of a formulation on the skin microbiome, since it alone allows a complete microbial ecosystem to be observed in its real physiological context, with its own inherent variability. But putting it into practice raises specific methodological choices: which sampling technique to use, how long to follow subjects, and whether to include self-sampling kits to expand the cohort. This guide details the options available for building a robust in vivo protocol.
Available sampling techniques
Three techniques dominate microbial sample collection in clinical studies, each with a different level of invasiveness and analytical depth:
- swabbing, the most common method, non-invasive, suited to repeated longitudinal monitoring of the same skin area;
- tape stripping, which collects the superficial layers of the skin using adhesive strips, providing more depth-stratified information on microbial colonization;
- minimally invasive punch biopsy, reserved for advanced clinical protocols requiring full tissue analysis, less suited to repeated sampling on the same subjects.
These techniques allow microbial communities to be sampled before and after application of the tested product, an essential condition for establishing an effect attributable to the formulation rather than to the subject’s natural variability.
Designing the study’s longitudinal follow-up
In vivo studies allow the microbiome’s dynamics to be tracked before and after application, over several weeks of treatment, assessing whether the tested formulations maintain microbial diversity and functional activity over time. This longitudinal follow-up is what fundamentally distinguishes an in vivo study from a one-off in vitro screening: it allows a trajectory to be observed, not just a state at a single point in time.
Integrating bioinformatics and statistical modeling is essential at this stage to differentiate the real treatment effect from natural inter- and intra-individual variability, which remains, as is well known, one of the main confounding factors in skin microbiome research.
Self-sampling: expanding accessibility and statistical power
At-home self-sampling kits, such as Sequential or Smart Probes™, expand the accessibility and sophistication of microbiome clinical trials. They allow subjects to perform their own sampling without traveling to a study center, which facilitates more frequent follow-up and a potentially larger, more geographically diverse cohort.
The table below compares the main sampling options depending on the study objective.
| Technique | Invasiveness | Suited to repeated follow-up | Main use case |
|---|---|---|---|
| Swabbing | Non-invasive | Yes, very well suited | Standard longitudinal follow-up, routine studies |
| Tape stripping | Non-invasive | Yes | Depth-stratified skin analysis |
| Punch biopsy | Minimally invasive | Limited | Full tissue analysis, advanced clinical protocols |
| Self-sampling kit (e.g. Sequential, Smart Probes™) | Non-invasive, at home | Yes, facilitates frequency | Large cohorts, decentralized follow-up, geographic accessibility |
What these choices mean for claim robustness
The choice of sampling technique and follow-up frequency should be decided based on the type of claim targeted: a “maintains microbial balance over time” claim requires a longitudinal design with several measurement points, whereas a one-off claim about an immediate effect can rely on a simpler before/after sample. Self-sampling, in particular, helps strengthen a study’s statistical power by expanding the cohort without excessively increasing logistical burden, a valuable asset for documenting the inter-individual variability already known to be high for this type of parameter.
To identify laboratories offering in vivo protocols and self-sampling solutions suited to your microbiome claim, the Skinobs platform references specialized providers.
Discover skin microbiome testing solutions on Skinobs → https://www.skinobs.com/
