John’s Evidence Score is a transparent editorial judgement about the strength of evidence for one precise essential-oil claim. It is not a medical effectiveness rating, a safety score or a recommendation to use the oil.
The score in one table
John’s Evidence Score rates the evidence for one precise claimed outcome. It is not an effectiveness guarantee, safety rating or treatment recommendation.
| Score | Meaning |
|---|---|
| 0 | No credible evidence found |
| 1-2 | Theory, tradition, laboratory or animal evidence only |
| 3-4 | Limited or poor-quality human research |
| 5-6 | Some encouraging human evidence, with important limitations |
| 7-8 | Several reasonably strong and consistent human studies |
| 9-10 | Strong evidence supported by authoritative reviews or clinical guidance |
How a claim is assessed
- Define the exact outcome. “Improves perceived sleep quality” is assessable; “treats insomnia” is a broader and much stronger claim.
- Start with the strongest available evidence. I prioritise clinical guidance, systematic reviews, meta-analyses and controlled human studies.
- Check whether the evidence matches the claim. I compare the studied population, preparation, dose, delivery method, comparator and outcome with what a reader might reasonably infer.
- Actively look for weaknesses. Small samples, inconsistent results, poor blinding, selective reporting and indirect laboratory evidence lower confidence.
- Keep safety separate. A supported effect is not proof that an oil is appropriate or safe for every person, animal, route or dose.
- Publish the reasoning. Every score appears with a verdict, limitations, cited sources and the date it was last reviewed.
What counts as human evidence?
Laboratory and animal studies can help explain a mechanism or identify a question worth testing. They cannot by themselves demonstrate a meaningful health benefit in people. I therefore describe them accurately but do not allow them to carry a human health claim.
Why the score may change
Evidence is not static. A larger trial, a better systematic review, a regulator’s assessment or an important safety signal may change the balance. The review date makes that uncertainty visible rather than hiding it.
Corrections and disagreement
Reasonable readers may weigh an imperfect evidence base differently. The point of the score is not to make the judgement infallible; it is to make the judgement inspectable. If a source has been misread or important evidence is missing, HealthWatchlist should correct the record and explain any material change.
Featured image: Researcher using pipettes by Rhoda Baer, National Cancer Institute · Public domain · cropped to 1200 × 675 and converted to WebP