Don’t take our word for it. Here’s every fact on this site, with its evidence grade, its caveats, and a link to the source, so you can check us.
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.
Indoor air / Measured in people or real products
Among 3,411 Czech households with an infant, the most commonly used chemical products were window cleaner (88%), deodorant (82%) and aerosol/hairspray products (74%), not air fresheners, which were the second-least-used of 18 chemical product categories (26%).
Moderate evidence: Self-reported product use frequency, one Central European cohort; product prevalence does not equal exposure dose or emission rate.
Source: Mikeš 2019, Science of the Total Environment Link to this fact
Indoor air / Measured in people or real products
A personal-care product containing the silicone D5 (such as a deodorant applied hours earlier) can raise D5 levels inside a car far above outdoor background, and this passenger-carried D5 vents out of the car and mixes with the vehicle's exhaust-associated emissions when the cabin fan runs.
Moderate evidence.
Caveats
Small controlled experiment (4 passengers, 1 vehicle, plus one deodorant-in-car test); a car cabin is a distinct, small, enclosed microenvironment, not home or building indoor air, which this paper does not measure.
Source: Coggon 2018, Environmental Science & Technology Link to this fact
Indoor air / Measured in people or real products
In a study of 60 UK homes with real air sampling (not a lab chamber), the VOC found in the highest concentration indoors was n-butane, an aerosol-spray propellant, not a fragrance chemical; it reached a wintertime maximum of 4,630 ug/m3, and aerosol antiperspirant/deodorant was the single most universally used VOC-releasing product, used in all 60 homes.
Moderate evidence: One UK town's panel-recruited cohort (Ashford, Kent); Givaudan-funded (fieldwork), analysis independent at University of York.
Source: Heeley-Hill 2021, Environmental Science: Processes & Impacts Industry-funded Link to this fact
Indoor air / Measured in people or real products
Of every ingredient/route combination in this deodorant risk assessment, the tightest safety margin was for inhaling didecyldimethylammonium chloride (DDAC), a quaternary-ammonium biocide, from spray deodorants used at home or in cars: its calculated margin of exposure was 30, only about 1.2 times the regulatory target of 25, driven by an unusually low reference concentration for DDAC rather than by high measured exposure.
Moderate evidence.
Caveats
Still above the regulatory safety threshold in this study's own framework (no risk was formally identified); a single Korean government assessment, modeled exposure rather than measured personal or biomonitoring exposure.
Source: Kim et al. 2018, Science of The Total Environment Link to this fact
Indoor air / Measured in people or real products
The plasma deodorant device itself generates ozone: about 1.5 ppm measured 3 cm from the outlet (roughly 7.5x the 15-minute occupational STEL of 0.20 ppm the authors cite), falling to about 0.16 ppm at 30 cm in a direct line and 0 ppm when the path to the sensor was blocked, which the authors say is below international occupational ozone limits at that distance.
Moderate evidence.
Caveats
Ozone measured by the device's own gas detector at fixed distances in open air with the device stationary; not measured as real personal breathing-zone exposure during actual underarm use, and occupational limits (TWA/STEL) were not designed for close-range personal-care-device exposure.
Source: Bok et al. 2024, Scientific Reports Link to this fact
Indoor air / Other evidence
For hairspray, deodorant, and eau de toilette sprayed at the head or upper body, about 85% of the sprayed product deposits on hair, skin, or other surfaces and only about 15% stays in the air available for inhalation, as a default in the absence of product-specific measurement.
Moderate evidence.
Caveats
The only cited direct measurement behind a comparable number is a 2012 deodorant/antiperspirant aerosol study (76.5-88.6% available for inhalation, i.e., 11.4-23.5% deposited) — a different, narrower product set than hairspray/eau de toilette.
Source: Steiling et al. 2025, Toxicology Letters Industry-funded Link to this fact
Indoor air / Other evidence
In the fragrance industry's 2015 aggregate exposure model, perfume, body spray, and deodorant spray were counted only as skin exposure; the paper reports no figure for how much is breathed in when a spray is used on the body.
Moderate evidence: Industry-funded paper by RIFM, Unilever, P&G, Givaudan and Firmenich staff; it shows the model did not estimate inhalation, not that inhalation is large or small.
Source: Safford et al. 2015, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Indoor air / Other evidence
The CIR draft applies its 'most spray droplets are not respirable' reasoning to polysorbate sprays at up to 4%, while admitting some evidence that deodorant sprays release substantially larger respirable fractions and that the information is 'not sufficient'.
Moderate evidence: Inhalation data are thin (one ethoxylated sorbitan laurate rat LC50); same boilerplate challenged in the CIR 2024 respiratory draft.
Source: CIR 2015 draft Industry-funded Link to this fact
Indoor air / Other evidence
In a lab chamber with a very high ozone level (about 6.5 ppm), all six ordinary perfumes, deodorants and cleaning liquids tested formed new particles; about 0.2% to 17% of the product's evaporated mass became aerosol, with an average near 4%.
Moderate evidence.
Caveats
One lab, six products, a closed 0.68 m3 chamber at roughly 100 times typical indoor ozone, very dry air, no vapor wall-loss correction; a yield, not an indoor concentration. NSF and Sloan funded; no industry funding.
Information, not medical advice. See also: myths we won’t tell you.