An independent, sceptical assessment of the research behind essential-oil claims: what looks promising, what remains unproven and what deserves caution.
How to read this matrix: Colours describe the strength of evidence for one specific claimed outcome. They do not mean that an oil is safe, medically recommended or a substitute for appropriate care.
| Claimed outcome | Lavender | Peppermint | Tea tree |
|---|---|---|---|
| Disinfects occupied indoor air | — | — |
Tea tree: Disinfects occupied indoor air
1/10 — Weak or unsupported
Laboratory antimicrobial findings do not show that diffusing tea tree oil safely disinfects a lived-in room or prevents human infection. Read the full Claim Review |
| Eases perceived nasal breathing discomfort | — |
Peppermint: Eases perceived nasal breathing discomfort
3/10 — Limited or mixed
Menthol can make breathing feel easier, but the limited evidence does not show that a peppermint-oil diffuser opens blocked airways or treats congestion. Read the full Claim Review |
— |
| Improves perceived sleep quality |
Lavender: Improves perceived sleep quality
6/10 — Limited or mixed
Lavender aroma may modestly improve how some people rate their sleep, but the evidence does not establish an effective treatment for insomnia. Read the full Claim Review |
— | — |
| Reduces short-term situational anxiety |
Lavender: Reduces short-term situational anxiety
6/10 — Limited or mixed
Inhaled aromatherapy may ease short-term anxiety in some clinical situations, but that is not evidence that a home diffuser treats an anxiety disorder. Read the full Claim Review |
— | — |
Inhaled aromatherapy may ease short-term anxiety in some clinical situations, but that is not evidence that a home diffuser treats an anxiety disorder.
Read the full Claim ReviewLavender aroma may modestly improve how some people rate their sleep, but the evidence does not establish an effective treatment for insomnia.
Read the full Claim ReviewMenthol can make breathing feel easier, but the limited evidence does not show that a peppermint-oil diffuser opens blocked airways or treats congestion.
Read the full Claim ReviewLaboratory antimicrobial findings do not show that diffusing tea tree oil safely disinfects a lived-in room or prevents human infection.
Read the full Claim ReviewNo assessed claims match those filters.
How I score the evidence
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 |
This matrix is a living research index. A grey cell means that I have not assessed that oil-and-outcome pairing; it does not imply that the claim is false. Scores can change when better evidence becomes available, and every assessed cell carries a last-reviewed date.
Featured image: Researcher using pipettes by Rhoda Baer, National Cancer Institute · Public domain · cropped to 1200 × 675 and converted to WebP