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.
Fragrance is everywhere / Self-reported survey
Among 718 non-smoking Saudi university students surveyed in 2020, 65.7% (472) reported using scented candles, and usage was far more common among women (74.9% of female respondents) than men (28.4% of male respondents, chi-square p=0.0001).
Moderate evidence: Convenience/snowball sample recruited via WhatsApp and Twitter, not a probability sample; may not generalize beyond young, social-media-active Saudi university students.
Source: Al Khathlan et al. 2023, BMC Public Health Link to this fact
Fragrance is everywhere / Other evidence
Researchers found multiple fragrance sources (cosmetics, air fresheners, cleaning/laundry products, fragrance-emitting devices, or candles) in every one of the 37 homes they surveyed for a chemical-intolerance study.
Moderate evidence.
Caveats
Sample is self-selected chemical-intolerance patients recruited from a specialty clinic, not a general-population sample; fragrance ubiquity may be overrepresented relative to the general population's home inventories.
Source: Rincón et al. 2024, Primary Health Care Research & Development Link to this fact
Information, not medical advice. See also: myths we won’t tell you.