Evidence levels A to D
In brief
Vegalab grades every source of evidence on four levels, A to D. The level says what kind of evidence it is and, more usefully, what it is allowed to support. The single rule that matters most: a finished-product claim rests on finished-product evidence.
The four levels
| Level | What it is | What it supports |
|---|---|---|
| A | Published literature on an ingredient, active or mechanism. | Explaining how an ingredient works. Describing what a body of research shows. Ingredient library entries. |
| B | Vegalab formulation and bench records: ingredient certificates, batch records, particle size, pH, viscosity, stability. | Composition, specifications and formulation facts, with the method stated. |
| C | Testing of the finished product by a third-party laboratory: skin hydration, moisture loss, elasticity, color, skin compatibility, preservative efficacy, microbial limits. | A defined product claim, worded to match the endpoint that was measured. |
| D | Clinical or regulatory validation: a controlled clinical study, or a regulator's published position. | The strongest wording available, limited to the validated endpoint. |
The rule: finished-product claims need finished-product evidence
A published trial of an ingredient used a specific concentration, a specific base and a specific population. A finished serum has its own concentration, base and pack, so it is tested in its own right.
So every ingredient page on this site carries the same line where literature is cited: "The studies below describe the ingredient itself." You will find it on entries such as niacinamide and hyaluronic acid. The line is the rule made visible.
What each level looks like on a page
Level A. "Niacinamide has been studied for the look of uneven tone." This describes research on the ingredient. It is published on ingredient pages.
Level B. "Centella asiatica extract is the second ingredient after water." This comes from the ingredient certificate for the formula. It is a composition fact.
Level C. A statement that skin hydration rose by a stated amount at a stated time, measured by corneometer. It is published only when a finished-product study exists, with the laboratory, the sample size and the limitations named beside it.
Level D. "FDA does not approve cosmetics." This rests on the regulator's own published position and the statute behind it.
Which level a claim needs
| Claim shape | Minimum level |
|---|---|
| Contains an ingredient | B |
| A stated percentage of an ingredient | B |
| A particle or capsule size | B, method stated |
| Hydrates, with no number | A and B together |
| A measured change in hydration, moisture loss, elasticity or tone | C |
| Suitable for sensitive skin | C, from a skin compatibility study |
| A preservation or microbial quality statement | C |
| Any comparison with another product | C or D, on both products |
A claim takes the level of the weakest source linked to it. An author cannot grade a claim upward. How the level C and B methods work is set out on how we test.
Rules that apply at every level
Sponsor disclosure. Every study page names who paid for the study. Where Vegalab commissioned it, the page says so.
Limitations are published. Every study page states the limitations of the study beside its result.
Consumer perception is labeled as perception. A percentage from a consumer questionnaire always carries the number of participants, the duration, and the statement that it is self-assessed.
Claims expire. Every register entry carries a review date. On that date the claim stops rendering until the Vegalab Beauty Science team has checked it again.
Where to go next
The evidence hub indexes every registered claim by formula. The science and claims charter sets out the limits we write to. The Hydrating dossier shows how the levels apply to one formula.
Frequently asked questions
Why is level A the lowest level if published research is strong?
Because it answers a different question. A well-run study on niacinamide tells you about niacinamide in the conditions of that study. A finished serum, with its own concentration, base and pack, is tested as a finished product.
Is level D always better than level C?
It is stronger for the endpoint it validated. A regulatory or clinical validation applies to that endpoint, that population and that product.
Can a claim move up a level?
Only when new evidence at the higher level exists and is linked to it. The register sets each claim's level from the weakest source linked to it, so a claim cannot be graded above its evidence.
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