Translating microbiome science into a compliant cosmetic claim remains a complex exercise. Unlike traditional cosmetic claims, microbiota-related claims require a clear understanding of terminology, the applicable regulatory landscape, and the evidence standards expected by authorities. This guide reviews what is permitted, what is prohibited, and the ethical precautions that should be built into the study protocol from the outset.
Microbiota and microbiome: a distinction that shapes the evidence
Accurate terminology is essential for both scientific rigor and regulatory compliance. Microbiota refers strictly to the collection of microorganisms present on the skin (bacteria, fungi, viruses, mites). Microbiome, on the other hand, extends beyond mere presence to include microbial function: the genetic material, metabolites, enzymes, and cell surface molecules that collectively interact with the host.
This distinction is not a semantic exercise: it directly shapes experimental design, claim language, and the type of evidence required for substantiation. A claim about composition (microbiota) does not call for the same study design as a claim about function (microbiome), which requires multi-omics analyses to document gene expression, proteins, and metabolite production.
What the European regulatory framework allows and prohibits
In Europe, EC Regulation No. 1223/2009 requires that all cosmetic ingredients, including live or inactivated microorganisms, be safe and non-toxic. On this basis, some claim formulations are allowed, others explicitly prohibited:
Generally permitted claims, provided they do not imply a therapeutic or medical benefit:
- “microbiome-friendly”;
- “supports the microbiota”;
- “maintains microbial balance”.
Currently prohibited claims:
- any formulation suggesting an enhancement of microbiome diversity;
- any formulation suggesting stimulation of microbial populations.
The ICCR (International Cooperation on Cosmetics Regulation) has also developed standard definitions that structure admissible regulatory language:
| Category | ICCR definition | What it implies for the study |
|---|---|---|
| Probiotics | Viable microorganisms intended to confer a cosmetic benefit | Prohibited in live form in finished products in the EU |
| Postbiotics | Inactivated microbial derivatives or metabolites | Allowed, require functional proof of benefit |
| Paraprobiotics | A subset of postbiotics, derived from inactivated microorganisms | Same evidence requirement as postbiotics |
| Prebiotics | Substrates that selectively nourish beneficial bacteria | Proof of selectivity and effect on commensal flora |
Compliance with these definitions ensures that a claim is both scientifically grounded and legally defensible.
A framework still fragmented at the international level
Global harmonization of skin microbiome-related regulations remains a work in progress. Regulatory differences between Europe, the United States, Korea, and Japan complicate the validation and commercialization of a single claim internationally. ICCR definitions provide a reference framework, but interpretation and enforcement vary by region. Terminology and methodology harmonization is therefore a direct issue for multinational brands seeking to maintain compliance while leveraging performance data already validated elsewhere. Ongoing collaborative initiatives between regulatory agencies and scientific consortia aim to standardize sampling methods, sequencing and analysis protocols, and the language defining each type of claim, a trend that will shape international product launches through 2027.
Ethical considerations: an often underestimated issue
Conducting a study on the skin, scalp, or hair microbiome requires adherence to strict ethical standards: informed consent, anonymization of genetic data, and safety of microbial exposure. Regulatory guidelines require that any probiotic, postbiotic, or prebiotic tested must not produce toxins and must be non-pathogenic. Ethical review boards generally require detailed protocols for in vivo studies, particularly when they target vulnerable populations such as infants or individuals with pre-existing skin conditions.
One point deserves particular attention when designing a study protocol: a study published in PNAS found that more than 80% of individuals could be re-identified from their skin microbiome profile alone within one year of sampling. The microbiome therefore constitutes, much like genetic data, sensitive personal data whose anonymization and governance must be handled with the same rigor as standard DNA sequencing.
To identify laboratories able to conduct studies compliant with these scientific, ethical, and regulatory standards, the Skinobs platform references providers specialized in microbiome claim substantiation.
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