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
What you can do / Self-reported survey
People affected by fragrance say policies work only with purchasing rules for fragrance-free, low-emission products, staff education, better ventilation, and consequences for repeat violations, enforced like smoke-free rules.
Weak evidence: Participants' and authors' proposals; not tested as an intervention.
Source: Roy 2026 Link to this fact
What you can do / Review of other studies
Fragrance-free policies are easier to make work when they start with a needs assessment and an inventory of the cleaning and personal products in use, involve employees in drafting, and agree how violations are handled before launch.
Weak evidence: Lessons from unnamed organizations; no outcome data.
What you can do / Review of other studies
Because people with MCS describe both a fear of asking for accommodations (risking hostility) and a fear of staying silent (risking worsening symptoms), workplaces and services that proactively offer fragrance-free accommodation without requiring the person to ask remove one source of this dilemma.
Weak evidence.
Caveats
Qualitative theme ('suppressing vs expressing needs', 9 findings/5 studies) describing participants' experience, not a tested intervention; no study in this review evaluated an accommodation policy's effect. Downgraded moderate→weak 2026-09-27 (Jev audit): the accommodation recommendation is an inference, not a finding.
Source: Driesen 2020, Journal of Psychosomatic Research Link to this fact
What you can do / Animal study
People who work for hours daily near burning scented candles under high job stress (for example, spa, hospitality, or restaurant staff who tend candle displays), rather than casual home users, are the population most directly addressed by this animal model, and may want to reduce burn time or improve ventilation in that specific occupational setting.
Weak evidence.
Caveats
Based on a single small, unreplicated mouse study using an occupational-intensity exposure chamber; no human occupational data were collected, and the specific candle's composition was not disclosed.
Source: Chandrasekaran 2021, Current Research in Toxicology Link to this fact
Information, not medical advice. See also: myths we won’t tell you.