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.
The industry / Measured in people or real products
The study's own authors note that current diagnostic patch-test concentrations for oxidized linalool allergy are more than 500 times higher than the hydroperoxide levels they actually found in consumer products.
Moderate evidence: Industry-funded interpretation; does not itself prove patch tests over-diagnose, since already-sensitized skin can react to much lower doses than the diagnostic test threshold.
Source: Kern 2014, Analytical and Bioanalytical Chemistry Industry-funded Link to this fact
The industry / Measured in people or real products
Despite thousands of positive allergy-test reactions to oxidized limonene and linalool reported worldwide, the fragrance industry's own market-testing program concluded that where people are actually getting exposed to these allergens "remains elusive" — the industry itself has not identified the real-world consumer-product source of a widely documented skin allergy.
Moderate evidence.
Caveats
This is the industry's own conclusion, from an industry-funded study; it does not mean the allergy is not real or not caused by fragrance chemicals — only that the specific consumer-product exposure route has not been chemically confirmed even by the party with the strongest incentive to find an innocuous explanation.
Source: Natsch 2019, Food and Chemical Toxicology Industry-funded Link to this fact
Information, not medical advice. See also: myths we won’t tell you.