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.
What you can do / Self-reported survey
About twice as many Australians would prefer fragrance-free workplaces (42.8%) as fragranced ones (22.2%), and over three times as many prefer unscented flights (57.7% vs 16.3%).
Moderate evidence.
Source: Steinemann 2017, Preventive Medicine Reports Link to this fact
What you can do / Self-reported survey
Most people would rather have fragrance-free spaces: 65% prefer fragrance-free airplanes, 61% hotels, 51% health care, and 48% workplaces, against 16-22% who prefer them fragranced.
Moderate evidence: Preference survey, adults 18-65.
Source: Steinemann 2019, Air Quality, Atmosphere & Health Link to this fact
What you can do / Self-reported survey
People with asthma back fragrance-free spaces by wide margins: 66.2% vs 16.1% for fragrance-free workplaces and 72.1% vs 14.8% for fragrance-free health care.
Moderate evidence.
Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact
What you can do / Self-reported survey
More UK adults prefer fragrance-free over fragranced workplaces (44.7% vs 23.3%), health care (43.3% vs 26.7%) and airplanes (61.9% vs 18.4%).
Moderate evidence: Pluralities, not majorities, for workplace and health care; preference, not health benefit.
Source: Steinemann 2018, Air Quality, Atmosphere & Health Link to this fact
What you can do / Review of other studies
Occupational lung specialists treating irritable larynx syndrome recommend a 'low-scent' workplace policy or respiratory protection to limit exposure to triggers.
Moderate evidence: Clinical recommendation, not tested as an intervention.
What you can do / Measured in people or real products
The California Department of Public Health recommends enforced fragrance-free workplace policies, no air fresheners or fragranced cleaners, and better ventilation instead of odor masking.
Moderate evidence: Recommendation from a public-health agency based on surveillance, not an intervention trial.
What you can do / Self-reported survey
A fragrance-free sign is not enough on its own: Canadians with chemical sensitivities described workplaces and hospitals with 'scent-free' policies where staff still wore scents and scented cleaners stayed in use.
Moderate evidence: Qualitative focus groups, n=60 self-selected MCS/IAQ-affected Canadians; advocacy-funded.
Source: Roy 2026 Link to this fact
What you can do / Review of other studies
Smell scientists reviewing the evidence found that scenting workplaces to boost mood or productivity is not well supported, and noted that a chemically intolerant employee can react to a fragranced workplace.
Moderate evidence: Short narrative review; the positive-scent literature it weighs is small; no primary data.
Source: Dalton & Jaén 2010, Current Opinion in Allergy and Clinical Immunology Industry-funded Link to this fact
What you can do / Self-reported survey
Support for fragrance-free health care and workplaces is not limited to people with symptoms: in Germany roughly 70% of those who backed them reported no fragrance-related health effects themselves.
Moderate evidence: Our arithmetic from Table 5; preference, not outcome; German workplace support was only 33.2% (30.6% against, 35.3% unsure).
Source: Klaschka 2020, Environmental Sciences Europe Link to this fact
What you can do / Government agency
Workplace accommodations for fragrance sensitivity do not have to be a building-wide ban: the US Labor Department's Job Accommodation Network lists scent-free meeting rooms, moving a worker away from air fresheners and vents, telework, air purifiers, signage, and staff education.
Moderate evidence: List of options, not tested for effectiveness.
What you can do / Measured in people or real products
Being below a standard occupational exposure limit does not mean an irritant gas is safe for someone with asthma: chamber studies found severe asthma attacks from sulfur dioxide and sulfuric acid at concentrations at or below typical workplace limits for those substances.
Moderate evidence: Occupational limits are set for healthy workers by design; this is not itself an argument that the limits are wrong, only that they don't protect people with asthma.
Source: Johansson 2016, Critical Reviews in Toxicology Link to this fact
What you can do / Review of other studies
When relying on a workplace, clinic, or school's fragrance-free policy, check whether it (1) defines what's covered beyond perfume, especially cleaning and laundry products, (2) sets a default fragrance-free expectation rather than a complaint-triggered one, (3) controls what cleaning/laundry products the institution buys, and (4) names a real consequence for non-compliance — a 2026 scoping review of 63 such policies found these structural features present in well under half of cases.
Moderate evidence: Based on a gray-literature document review of North American policies; individual policies may vary, and having these features on paper does not guarantee enforcement.
What you can do / Review of other studies
Aluminum-salt antiperspirants (aluminum chlorohydrate and related salts) work by two combined mechanisms: they physically plug sweat ducts by polymerizing into a gel at skin pH, and they directly inhibit the growth of odor-causing skin bacteria; fragrance is not the active mechanism.
Moderate evidence: Mechanism review synthesizing older primary studies; does not itself measure sweat reduction or bacterial counts in a new trial.
Source: Kanlayavattanakul & Lourith 2011, International Journal of Cosmetic Science Link to this fact
What you can do / Government agency
EPA's official framework for improving indoor air quality ranks three strategies in order: (1) source control (remove or reduce the pollutant source), (2) increased ventilation, and (3) air cleaners, which EPA says are far more effective for particles than for gaseous pollutants.
Moderate evidence: Agency guidance/assertion, not a controlled comparison of the three strategies.
Source: US EPA, "The Inside Story" Link to this fact
Information, not medical advice. See also: myths we won’t tell you.