Every fact on this site, with its evidence grade, its caveats and a link to the source.
We start you on the strong ones: findings that have been replicated or come from one large, well-controlled study. Moderate and weak facts are here too, labeled for what they are. Use “Link to this fact” to share a single card.
Green, natural and unscented / Measured in people or real products
'Natural' oils get no special protection from air: in lab tests, lavender oil's main scent chemicals oxidized just as fast as a synthetic copy made only of those chemicals, and formed the same allergenic hydroperoxides.
Strong evidence: Lab chemistry, neat oil in open flasks over 10-45 weeks; one oil type (lavender), two batches.
Source: Hagvall 2008, Contact Dermatitis Industry-funded Link to this fact
Information, not medical advice. See also: myths we won’t tell you.