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.
Health effects / Review of other studies
No published study has been found that tests whether quaternary ammonium compounds specifically from laundry fabric softeners or dryer sheets, as opposed to disinfectant or cosmetic-preservative exposure, cause asthma or skin sensitization in consumers.
Weak evidence: This is an evidence-gap statement, not a positive finding; the review also never discusses esterquats, the ester-linked chemistry that dominates modern fabric softeners, at all.
Source: Peyneau 2022, Frontiers in Toxicology Link to this fact
What you can do / Review of other studies
If households switch from fragranced to fragrance-free laundry detergent, modeling suggests dryer-vent limonene emissions across a whole city or state could drop substantially — an estimated 1.58 tons per year for metropolitan Melbourne, or 8.66 tons per year for the state of California.
Weak evidence.
Caveats
This is a modeled extrapolation, not a measurement: it multiplies a mean vent concentration from just 2-6 households (one grab sample each) by census household counts and usage-rate assumptions, with no confidence interval or sensitivity analysis anywhere in the calculation; the Melbourne input is dominated by a single outlier household roughly 11 times the other three.
Source: Goodman, Nematollahi & Steinemann 2020/2021, Air Quality, Atmosphere & Health Link to this fact
Information, not medical advice. See also: myths we won’t tell you.