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 / Self-reported survey
Diffusing a scent in the bedroom air was linked to better self-reported sleep quality and less next-day tiredness than a pillow spray or no scent at all, in a small industry-funded trial of healthy adults, but this has not been shown to improve sleep as measured objectively.
Weak evidence.
Caveats
N=39 diffuser vs 19 control; one of the two reported p-values (0.052) is above the paper's own significance threshold; non-randomized; no air-quality/VOC measurement of what the diffuser actually released; funded by Takasago Europe.
Source: Li et al. 2025, Scientific Reports Industry-funded Link to this fact
Health effects / Other evidence
Dermatologists consider moisturizer use critical for preventing and treating numerous skin conditions, and regard allergic or irritant contact dermatitis as the only established health risk of moisturizer use.
Weak evidence.
Caveats
This is the study authors' Discussion-section opinion, not a result of the underlying label survey, and not a formal quantitative risk-benefit analysis weighing skin-barrier/disease-prevention benefits against contact-dermatitis risk. It also covers moisturizers only — no equivalent risk-benefit statement for sunscreen specifically (weighing skin-cancer prevention against contact-dermatitis risk) was found in our evidence base or in this pass, so the video's sunscreen half of the claim remains unsupported by our evidence.
Health effects / Self-reported survey
In the same study, migraineurs with interictal olfactory hypersensitivity (IOH, 16/113) had markedly LOWER rates of osmophobia (75% vs 98%, P=.002) and odor-triggered crisis (68% vs 93%, P=.001) than those without IOH, but markedly HIGHER rates of phantosmia (25% vs 1%, P=.001) and cacosmia/euosmia (18% vs 0%, P=.002) — the opposite direction from the positive IOH-osmophobia association reported by Demarquay et al. 2006.
Weak evidence.
Caveats
Small IOH subgroup (n=16), single study, directly contradicts an earlier primary (Demarquay 2006, not yet in this evidence base); the authors themselves call the discrepancy unexplained and note their IOH question differs from Demarquay's validated chemical odor intolerance index.
Source: Fornazieri 2016, Headache: The Journal of Head and Face Pain Link to this fact
Health effects / Other evidence
Nail salon workers have reported elevated rates of headaches, respiratory irritation, skin problems, and nasal/airway symptoms in prior cross-sectional surveys, consistent with (but not directly tested by) this study's indoor air quality measurements.
Weak evidence: This paper measured air chemistry only, not health outcomes; the symptom literature it cites is cross-sectional survey data from other studies.
Source: Pavilonis, Roelofs & Blair 2018, citing prior nail-salon worker surveys, Journal of Occupational and Environmental Hygiene Link to this fact
Health effects / Other evidence
The TVOC and PM2.5 increases measured after cleaning in this study (up to about 104 ppbv and 14.5 micrograms per cubic meter) fall at the lower end of ranges reported elsewhere for cooking (10-560 ppbv, 0.3-480 micrograms per cubic meter) and smoking (up to 600 ppbv, up to 253 micrograms per cubic meter).
Weak evidence.
Caveats
The cooking/smoking numbers are secondhand citations from other studies, not measurements from this paper, and the authors note their own small-surface controlled experiments likely understate real-world cleaning exposure (e.g., multiple surfaces cleaned in succession, as in the hotel).
Source: Souza 2025, ACS Earth Space Chem, ACS Earth and Space Chemistry Link to this fact
Health effects / Review of other studies
In one study, (R)-(-) and (S)-(+) linalool at concentrations below participants' own detection threshold — undetectable, not perceived as different — produced opposite heart-rate and mood changes, the one result in Herz's 18-study review that offers direct evidence for a chemical (pharmacological) rather than a learned-association mechanism.
Weak evidence: Single study, not independently replicated elsewhere in the review's own 18-study set; Herz's overall conclusion still favors the psychological account for the other 17 studies.
Source: Kuroda et al. 2005, via Herz 2009, International Journal of Neuroscience Industry-funded Link to this fact
Hidden ingredients / Measured in people or real products
Acetaldehyde, a possible human carcinogen (IARC Group 2B), was released by 23 of 42 baby products and was never listed on any label.
Weak evidence: Not quantified; may partly form during 40 C incubation.
Source: Nematollahi 2018, Air Quality, Atmosphere & Health Link to this fact
Hidden ingredients / Review of other studies
As early as 2004, a letter in Environmental Health Perspectives warned that fragrances can draw on thousands of chemicals and that most fragranced products had never been tested for human toxicity.
Weak evidence.
Caveats
The '4,000' figure comes from a 1991 book (Ashford & Miller) and describes untested products, not chemicals; later counts run ~3,000. Date 2020, now read as primary, corroborates 'thousands' as the right order of magnitude for the RIFM inventory (~2,600 active + ~3,500 discontinued) and separately states many individual fragrance materials lack toxicity data for standard endpoints — closer to Curtis's 'never tested' claim than any inventory count — but that is about individual chemicals with read-across-fillable data gaps, not about untested products, and does not confirm Curtis's specific '>4,000' figure.
Source: Curtis 2004, Environmental Health Perspectives Link to this fact
Hidden ingredients / Journalism
Laboratory testing commissioned by US campaigners found 38 chemicals not listed on the label across 17 popular fragrances, 14 per product on average, including hormone-disrupting synthetic musks.
Weak evidence: NGO report reproduced in a review; cite Sarantis 2010 directly; primary not in our evidence base.
Source: Sealey 2016 (citing Sarantis 2010, Not So Sexy), Environment International Link to this fact
Hidden ingredients / Other evidence
A 2015 student lab analysis of 12 popular US perfumes and body sprays found 14-33 separate organic chemicals in each product (130 in all), while US law lets the label say just "fragrance".
Weak evidence: Identities are unconfirmed library matches and were never published; counts depend on the detection threshold. Pair with Steinemann 2011 rather than citing alone.
Source: Lee 2015, Young Scientist Journal (Vanderbilt University) Link to this fact
Hidden ingredients / Measured in people or real products
In a university lab test, 3 of 4 cheap generic or dollar-store plug-in air fresheners gave off petroleum-type solvents (alkanes, one with n-hexane) and the fourth was mostly ethanol; none of these adds scent or appears on the package, and the brand-name plug-ins tested showed neither.
Weak evidence: Student journal; one unit per product; identities not confirmed with standards; no amounts measured.
Source: Pino-Delgado 2021 (J Student Res), Journal of Student Research Link to this fact
Hidden ingredients / Government agency
The industry safety panel's own risk calculation for PFOA (a persistent 'forever chemical' associated with PTFE manufacture) in lipstick relies on a single chemical supplier's claim of under 25 parts per billion in the raw material before it is formulated into a product — no actual PTFE-containing lipstick was tested for PFOA.
Weak evidence.
Caveats
The <25 ppb figure and the resulting '755-fold below EPA's advisory' conclusion are worst-case arithmetic on an unverified, pre-formulation raw-material claim, not a measurement of any real cosmetic product.
Source: CIR 2018 Industry-funded Link to this fact
Hidden ingredients / Industry source
PTFE (Teflon) is reportedly used in some cosmetics at concentrations up to 30%, more than double the 13% leave-on maximum cited from the industry-funded Cosmetic Ingredient Review.
Weak evidence.
Caveats
The paper's own use-concentration data for most PFAS ingredients 'differed by orders of magnitude' across sources; the specific source and current-market relevance of the 30% figure could not be verified for this ingest, and it may reflect a patent-claimed rather than marketed formulation.
Source: Balan 2024, Environmental Science & Technology Link to this fact
Hidden ingredients / Other evidence
Antiperspirants can contain 20-45% D5 (cyclopentasiloxane) by weight, and some leave-on hair serums are D5-dominant products.
Weak evidence: Figures come from a cited third-party product survey, not this paper's own chemical analysis of product formulations.
Source: Montemayor 2013, Chemosphere Industry-funded Link to this fact
Hidden ingredients / Review of other studies
Citing Uhde & Schulz (2015), more than 90% of substances in tested fragranced products were not declared on labels, and neither the FDA nor EU authorities have the resources to evaluate ingredient safety in all scented products on the market.
Weak evidence: Secondhand citation of a study not independently read for this evidence base entry.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Hidden ingredients / Government agency
Cosmetics Europe describes its COSMILE Europe database as giving consumers "reliable, verified and scientifically supported information" on almost 30,000 cosmetic ingredients, but its own press release does not name any data source or independent verification method for that content.
Weak evidence: Absence of a stated methodology in this press release does not itself mean the database is inaccurate; it means the accuracy claim cannot be checked from this document alone.
Source: Cosmetics Europe 2023 Industry-funded Link to this fact
Hidden ingredients / Review of other studies
In a 2007 NRDC test of 14 US air fresheners, 12 (86%) — including some labeled 'all-natural' or 'unscented' — emitted phthalates at up to 7,307 ppm, and none listed a phthalate on the label.
Weak evidence.
Caveats
NRDC 2007 is gray literature (an advocacy-group test, not peer-reviewed) and is not itself in our evidence base; this relays it secondhand through a 2017 review. Only 14 products tested, almost 20 years ago, so 86% is not a figure for the current market or for air fresheners in general. Peer-reviewed testing (Dodson 2012) separately confirms air fresheners are among the highest-DEP product categories, but does not reproduce this specific percentage.
Source: NRDC 2007 (via Steinemann 2017), Building and Environment Link to this fact
Indoor air / Measured in people or real products
In a week-long study of 7 working adults in Leipzig, the air at home made up 42-73% of the airborne chemicals they breathed, more than the outdoor air or their workplaces.
Weak evidence: N=7, one week, 25 VOCs; home share includes infiltrated outdoor air.
Source: Gokhale 2008, Science of the Total Environment Link to this fact
Indoor air / Measured in people or real products
In a real shower test, limonene in the bathroom air rose to about 80, 150, and 380 ppb as the amount of shower product went up, roughly in proportion to the amount used.
Weak evidence: One participant, one bathroom, PTR-MS; limonene only; peaks last minutes.
Indoor air / Hypothesis
A computer model of a morning shower found fragrance terpenes from the products react with indoor ozone to make formaldehyde (about +4 ppb), other aldehydes, irritant PAN-type nitrates, and a little fine particle matter, even with strong ventilation.
Weak evidence: Modeled (INDCM), not measured; increments are small and last about an hour; water-soluble products may dissolve in shower water, so these are upper limits.
Indoor air / Animal study
A continuously running essential-oil diffuser is now the exposure pattern with an animal result attached to it: continuous ambient lavender exposure advanced puberty in rats, while a larger once-daily nasal dose did not.
Weak evidence: Neither exposure was quantified, so the comparison shows a pattern, not a dose-response; with five animals per group the difference rests partly on one outlier.
Source: Kim & Lim 2022, Journal of Korean Medical Science Link to this fact
Indoor air / Instrument measurement
In a small closed test room, three short bursts of aerosol hairspray pushed fine-particle (PM2.5) readings to about 90 µg/m³, roughly 2.5 times the US 24-hour outdoor standard, though only for minutes.
Weak evidence: Uncalibrated consumer monitor; tiny room; short peak vs 24-h standard; primary spray aerosol, no fragrance characterized.
Indoor air / Measured in people or real products
A fresh, 10-minute-old mixture of limonene and ozone, at concentrations close to the high end measured in real homes and offices, made people's eyes blink significantly more often in a small controlled study, at roughly 2,000 times less limonene than pure limonene alone needs to irritate eyes.
Weak evidence.
Caveats
This is the paper's own LOEL (residual 0.23 mg/m3 limonene + 0.08 mg/m3 ozone, +17%, p=0.003) and was previously mis-cited on our evidence base to Klenø & Wolkoff 2004. Now verified as primary, but the same lab's own comparable re-test of Klenø & Wolkoff 2004 gave a 3.5x smaller effect (12% vs 42%) at nearly identical residual concentrations, and no dose-response held across the paper's own four LOPs mixtures (R2=0.7, ns).
Indoor air / Measured in people or real products
Methacrolein, a known limonene/isoprene ozonolysis product, produced a similarly-sized eye-blink-frequency increase on its own (+18% at 286 ppb) as the freshly reacted limonene-ozone mixture did, supporting the idea that it is reaction products, not parent limonene, that irritate eyes.
Weak evidence.
Caveats
Methacrolein was tested alone, not measured inside the LOPs mixtures, so this is an analogy of magnitude, not a demonstration that methacrolein specifically drives the limonene-ozone effect. Single small study, single lab.
Indoor air / Measured in people or real products
Whether an office air-conditioning filter was new or had been in service for about 10 months made no measurable difference to ozone or particle chemistry, or to occupants' reported symptoms, during ozone-limonene exposure.
Weak evidence.
Caveats
Compares only new vs. moderately used (MERV 13) filters at fixed ventilation/recirculation rates; does not test badly fouled filters or other filter grades, so it should not be read as showing filter replacement is never protective.
Indoor air / Review of other studies
During ordinary house cleaning with bleach, chlorine gas concentrations can peak at up to about 0.5 parts per million, and trichloramine is thought to reach similar concentrations when bleach reacts with ammonia or other nitrogen-containing substances.
Weak evidence: This is the authors citing a separate domestic-cleaner cohort study (their own ref. 15) as background, not a measurement made on the children or homes in this study.
Source: Nickmilder, Carbonnelle & Bernard 2007, Pediatric Allergy and Immunology Link to this fact
Indoor air / Measured in people or real products
A single portable air cleaner's benefit reached into a nearby room without its own cleaner, cutting PM2.5 by about 58% and PM10 by about 60% on average, though this secondary-room reduction did not reach statistical significance across the whole sample.
Weak evidence: Overall WSRT p=0.089 (PM2.5) and p=0.114 (PM10) in the secondary room; only the daytime-only comparison was borderline significant (p<0.1).
Source: Lu 2024, Aerosol and Air Quality Research Link to this fact
Indoor air / Lab study (cells or chemistry)
This study's in vitro bronchial-cell BKC aerosol doses used for transcriptomics (40.5-634.8 ng/cm2, derived from real commercial disinfectant concentrations of 0.1-0.4% BKC) are roughly comparable in order of magnitude to independently estimated human nasal-spray epithelial doses from approved BKC-preserved pharmaceutical products (about 90-3,020 ng/cm2, per Johnson 2018), unlike many mechanistic-study doses in the wiki that sit orders of magnitude above measured real-world exposure.
Weak evidence.
Caveats
Cross-source, order-of-magnitude comparison only: the product type (disinfectant vs. pharmaceutical), BKC concentration, tissue (bronchial vs. nasal) and deposition model all differ between the two studies, so this is not a validated equivalence.
Source: Kim et al. 2025, Ecotoxicology and Environmental Safety Link to this fact
Indoor air / Review of other studies
Benzo[a]pyrene levels in fumes from 12 tested scented candles ranged from 0.1 to 7.5 ng/m3, against a WHO guideline value of 1 ng/m3.
Weak evidence: Secondhand citation from this review (Orecchio 2011 not independently read for this evidence base); not this paper's own measurement.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Indoor air / Review of other studies
Measured benzene and naphthalene concentrations emitted by burning candles were reported below the standards considered to exert a toxic biological effect, while sulfur dioxide and benzopyrene concentrations might exceed recommended values in some tested candles.
Weak evidence: Secondhand summary of multiple chamber studies (Derudi, Orecchio) not independently read for this evidence base; heterogeneous across candle brands/types.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Indoor air / Other evidence
Burning scented candles indoors can release formaldehyde, CO2, and volatile organic compounds at levels above indoor background.
Weak evidence: Cites a secondary source (an air-freshener book chapter) not otherwise in this evidence base; not independently checked here against primary chamber measurements.
Source: Nazir et al. 2024, Annals of Medicine & Surgery Link to this fact
Indoor air / Measured in people or real products
Lighting one scented candle for 5 minutes in an ordinary room raised PM10 near the candle (1.52x baseline, 39.9 ug/m3) and kept PM2.5/PM1 elevated for a full hour 3 m and 6 m away (up to 1.97x baseline, ~26-31 ug/m3), with all measured peaks staying below Korea's 24-hour indoor air quality guideline (100 ug/m3 PM10, 50 ug/m3 PM2.5).
Weak evidence.
Caveats
Pilot study of 3 residential houses, one unspecified scented candle burned once for 5 minutes; no replication across candle types, scents, or house configurations, and no chemical (VOC/PAH) measurements.
Source: Yun et al. 2025, Scientific Reports Link to this fact
Indoor air / Measured in people or real products
Finer particles (PM2.5, PM1) from a lit scented candle did not simply decay with distance: their concentration kept rising over the hour measured at 3 m and 6 m from the candle, while PM10 peaked and declined fastest at the candle itself, consistent with warm particle-laden air traveling along the ceiling into adjacent spaces (the Coanda effect).
Weak evidence.
Caveats
Single pilot measurement per location per house (3 houses); mechanism (Coanda effect) is the authors' interpretation, not directly visualized or measured (e.g., no airflow tracer or thermal imaging).
Source: Yun et al. 2025, Scientific Reports Link to this fact
Indoor air / Measured in people or real products
After lighting a scented candle, a nano-sized bacterial extracellular vesicle population (Phyllobacterium myrsinacearum n-ABE) rose from a minor pre-burn component to 23.8-24.0% relative abundance at the candle spot and 6 m away, the first reported detection of this species' extracellular vesicles in indoor air; the authors attribute this to heat/combustion-triggered growth or apoptosis of the existing airborne bacterial population, not a new bacterial source.
Weak evidence.
Caveats
Single pilot study (3 houses), no independent no-candle control run in parallel (before/after design only), no health-outcome or exposure-dose measurement, and the growth-vs-apoptosis mechanism is the authors' proposed interpretation rather than a directly demonstrated causal pathway.
Source: Yun et al. 2025, Scientific Reports Link to this fact
Indoor air / Measured in people or real products
In the one NASA 1989 defoliation test (Marginata, benzene), the plant with all its leaves cut off removed slightly MORE benzene from the sealed chamber over 24 hours (70%) than the same species with full foliage (66%), suggesting root/soil microorganisms, not leaves, did most of the removal.
Weak evidence: Single species tested this way (n=1 comparison), report itself says the mechanism 'cannot be fully explained at this writing'.
Source: Wolverton 1989 Link to this fact
Indoor air / Measured in people or real products
Thermal degradation and combustion of styrene-containing polymers (such as polystyrene) releases styrene into the air; in one measurement of smoke from municipal structural fires, styrene along with benzene, toluene, naphthalene, and 1,3-butadiene accounted for 31% of total VOC concentration.
Weak evidence.
Caveats
Single cited study (Austin et al. 2001) of structural-fire smoke, not candle combustion or routine household conditions; IARC 2019 does not discuss candles specifically and this should not be extended to a candle-specific claim.
Source: IARC 2019 (Vol. 121) Link to this fact
Indoor air / Government agency
EPA warns that overwatered indoor houseplants can promote growth of microorganisms in the soil that may affect allergic individuals.
Weak evidence: Assertion, no measurement or citation given.
Source: US EPA, "The Inside Story" Link to this fact
Indoor air / Review of other studies
Diethyl phthalate (DEP), the phthalate most consistently tied to fragrance use, has been detected in household dust in a German study, alongside the plasticizer phthalates DEHP, DINP, and DBP.
Weak evidence.
Caveats
Relayed secondhand through Crinnion 2010, a narrative review in a naturopathic-medicine journal already flagged elsewhere in this evidence base for reproducing outdated/imprecise figures; the underlying German house-dust study itself is not in our evidence base and has not been checked directly. Presence in dust does not establish that fragrance products (rather than other DEP sources, e.g. plastics) are the dust's source, and does not establish an ongoing-exposure mechanism or a health effect.
Source: German house-dust study, via Crinnion 2010, Alternative Medicine Review Link to this fact
Indoor air / Measured in people or real products
In a two-week home-exposure study of 8 people, everyone had stopped noticing a constant pleasant household odor within two weeks, but when the odor was removed, only half had fully regained their sense of it after another two weeks, and one person had not recovered at all.
Weak evidence.
Caveats
N=8, single small study (Dalton & Wysocki 1996) described secondhand by this review; its exact participant count and odorants conflict with how the same senior author's own 2000 review describes an apparently related dataset (n=10, different odorants) — see C367.
Source: Pellegrino 2017, Physiology & Behavior Industry-funded Link to this fact
The industry / Journalism
The first press coverage of a 2011 study finding 133 undisclosed chemicals in 25 best-selling scented products, in the US government's environmental-health journal, quoted no manufacturer or industry group; the underlying numbers should be cited from the study itself (Steinemann 2011).
Weak evidence: Media-coverage note only; all product numbers belong to the primary src-2011-fragranced-consumer-products-chemicals-emitted-ingredients-unlisted.
Source: Potera 2011 (EHP news), Environmental Health Perspectives Link to this fact
The industry / Review of other studies
The fragrance industry's answer to autoxidation is to add antioxidants to linalool and linalool-rich natural extracts, but the Gothenburg researchers say that protection is hard to control.
Weak evidence: Industry practice via personal communication from a RIFM scientist (A. M. Api) in a RIFM co-funded paper; no data on effectiveness.
Source: Hagvall 2008, Contact Dermatitis Industry-funded Link to this fact
The industry / Animal study
Two common fragrance ingredients, hexyl and benzyl salicylate, may test positive in the mouse skin-allergy assay not because they are true human sensitizers, but because of a mouse-specific irritant/pharmacological effect, similar to a known false-positive detergent (sodium lauryl sulfate).
Weak evidence.
Caveats
A hypothesis proposed by structural-alert absence and analogy only; the paper offers no direct evidence (e.g., a biomarker distinguishing true haptenation from irritant-driven lymph node activity) and the underlying data are RIFM's own unpublished proprietary dataset.
Source: Roberts & Api 2018, Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
The industry / Review of other studies
The detergent industry's own risk assessment for esterquat fabric softeners sets a margin of exposure of about 8,100 (NOAEL 300 mg/kg bw/day vs. an aggregate consumer exposure estimate of 36.9 micrograms/kg bw/day) and concludes esterquats in fabric conditioner are safe for consumer use.
Weak evidence.
Caveats
Every number comes from the industry's own unpublished, unnamed studies with no independent citation trail; the exposure model covers only dermal and minor oral routes (no inhalation route at all, despite fabric conditioner being used in heated dryers); no carcinogenicity study and no multigeneration reproductive study exist for esterquats — the 'safe' conclusion infers these endpoints are unnecessary from adjacent negative results rather than testing them directly.
Source: HERA Project 2008 (A.I.S.E./CEFIC) Industry-funded Link to this fact
The industry / Review of other studies
The author of a 2023 clinical review arguing that chemical sensitivity is primarily psychogenic (not caused by product chemistry) previously received partial, later-withdrawn funding for an uncompleted IEI genetics study via an unrestricted grant from the Research Institute for Fragrance Materials, the fragrance industry's own research and trade body.
Weak evidence.
Caveats
The funding is disclosed by the author, was withdrawn before the study was completed (due to poor enrollment, not a documented data or conclusions issue), and does not by itself invalidate the paper's clinical arguments; it is a conflict-of-interest fact worth weighing, not proof of bias in this specific manuscript.
Source: Binkley 2023, Journal of Allergy and Clinical Immunology: In Practice Industry-funded Link to this fact
The industry / Review of other studies
This commentary on benzalkonium chloride's adverse effects on the nasal mucosa was funded by an educational grant from AstraZeneca USA, a pharmaceutical company with a commercial interest in intranasal corticosteroid products, which the same commentary recommends as the preferred alternative to decongestant sprays for allergic rhinitis.
Weak evidence.
Caveats
Funding disclosed in the acknowledgment; the underlying rhinostereometry trials (1995-1996) predate this 1999 funded commentary, so only the commentary's framing/synthesis, not the trial data, is implicated.
Source: Graf 1999, Clinical Therapeutics Industry-funded Link to this fact
The industry / Other evidence
This review of BAK's harms to the trabecular meshwork was partly funded by Merck, Inc., and its senior author, Paul Kaufman, discloses paid consultant, honoraria, and financial-support relationships with Alcon and Allergan, both manufacturers of BAK-free alternative eye-drop preservatives (SofZia and Purite respectively) that the review discusses favorably.
Weak evidence.
Caveats
This is a conflict-of-interest disclosure, not an evidentiary finding. The funding pattern runs opposite to a typical 'industry defends its own product' case: the paper argues against a preservative (BAK) while its senior author has financial ties to companies selling competing, BAK-free alternatives.
Source: Rasmussen et al. 2014, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact
The industry / Review of other studies
This benzalkonium chloride pulmonary-toxicity review was written by a single author with no coauthors and no named funding source, who is the principal of a private toxicology consultancy (Pharma Toxicology Safety Solutions LLC) whose business is toxicology/regulatory consulting typically for pharmaceutical clients; the article declares no competing financial interests but gives no funding statement either way.
Weak evidence.
Caveats
This is a characterization of authorship and potential conflict of interest, not a toxicology finding; the review's consistent framing (reinterpreting adverse animal/in vitro findings as clinically inapplicable, and concluding regulatory tightening is unwarranted) matches the argumentative pattern common in industry-oriented safety literature, but no direct pharma-company funding or engagement was found or disclosed.
Source: Johnson 2018, Journal of Aerosol Medicine and Pulmonary Drug Delivery Link to this fact
The industry / Review of other studies
The study authors cite an earlier analysis reporting that some commercially available PTFE powders contained more than 400 ppb of PFOA — 16 times the EU's 25 ppb regulatory limit — indicating PFOA contamination has been found in the market, not only in controlled lab experiments.
Weak evidence.
Caveats
This is a citation within the primary paper (attributed to Larsen et al. 2005, Analyst) that this evidence base has not independently read or verified; no product names, brands, or cosmetic use are identified.
Source: Oshima et al. 2020, Scientific Reports Industry-funded Link to this fact
The industry / Review of other studies
According to an industry report cited in this review, about 75% of scented candles are fragranced with artificial scents because they cost less than natural fragrance materials.
Weak evidence: Cited without an independently checkable primary source in this review; industry-report figure (ref. 48).
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
The industry / Review of other studies
One of this 2024 axillary-dermatitis review's three authors discloses paid consulting, honoraria, or equity relationships with multiple cosmetic- and pharmaceutical-adjacent companies, including the industry-funded Cosmetic Ingredient Review panel.
Weak evidence.
Caveats
Disclosed conflict of interest is at the individual-author level, not a study funding source; the review's factual content was not evaluated differently on this basis, but the affiliation is named for transparency.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
The industry / Other evidence
The US market for scented candles is estimated to be worth approximately $2 billion annually.
Weak evidence: Abstract-only/background figure; sourced from an industry-characterization paper (Ahn et al. 2015) not independently verified in this evidence base.
Source: Nazir et al. 2024, Annals of Medicine & Surgery Link to this fact
The industry / Measured in people or real products
A 2022 Korean study proposes prioritizing the specific hormone-disrupting chemical combinations that most often turn up together in household products, rather than testing chemicals one at a time, for future mixture-toxicity testing and regulatory management.
Weak evidence: This is a testing-prioritization proposal based on ingredient co-occurrence, not new toxicity data showing that any of the proposed mixtures cause harm.
Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact
The industry / Other evidence
A study by Petry et al. (2014) concluded that, under normal conditions of use, scented candles do not pose known health risks to consumers.
Weak evidence.
Caveats
Petry et al. 2014 is now a evidence base primary (src-2014-health-risk-evaluation-selected-voc-svoc-particulate). Its Conflict of Interest statement reads: "Financial support for this work has been provided by a consortium of companies organized by the Research Institute for Fragrance Materials Inc. (RIFM)." All eight authors are affiliated with ToxMinds, RIFM, SC Johnson, Firmenich, Procter & Gamble or Reckitt Benckiser. It is one study among several in this same Viewpoint reaching the opposite conclusion (Adamowicz 2019, Derudi 2014, Chandrasekaran 2021), and its own 'no known health risk' conclusion did not test acrolein or NO2 and used a PAH detection limit too coarse to find the BaP levels a later, comparably funded sibling study (Salthammer 2021) measured exceeding WHO guidance.
Source: Singh 2023, Environmental Science & Technology Link to this fact
The industry / Other evidence
An earlier FDA-lab study found that musk xylol, a synthetic musk fragrance ingredient, did move out of a 24-hour skin reservoir and into the bloodstream over time, unlike the self-tanner and hair-dye chemicals in the 2004 follow-up study.
Weak evidence: Cited secondhand from Yourick 2004's discussion; the Hood 1996 primary source has not been independently read and ingested into this evidence base.
Source: Hood 1996, cited in Yourick 2004, Toxicology and Applied Pharmacology Link to this fact
Laws and loopholes / Journalism
As of 2010, the US FTC's Green Guides on environmental marketing claims had not been updated since 1998.
Weak evidence: Outdated: the Green Guides were revised in 2012 (and an update was proposed in 2022); do not use as a current fact.
Source: Dahl 2010, Environmental Health Perspectives Link to this fact
Laws and loopholes / Review of other studies
Fewer than 20% of the roughly 3,000 high-production-volume (HPV) chemicals in the US have been tested for potential to cause developmental neurotoxicity.
Weak evidence.
Caveats
Sealey 2016 relays this figure faithfully from Landrigan 2010, but Landrigan 2010's own citation to Goldman 1998 (Environ Health Perspect), now read directly in this evidence base (src-1998-chemicals-childrens-environment-risks), is not supported: Goldman 1998 contains no '20%' statistic and no developmental-neurotoxicity-specific testing figure. Its actual EDF-sourced figures (71% no basic toxicity data at all, 63% not tested for carcinogenicity, <50% tested for any chronic toxicity) describe different, broader endpoints.
Source: Sealey 2016 (citing Landrigan 2010), Environment International Link to this fact
Laws and loopholes / Measured in people or real products
Musk ambrette, banned in the EU for years, was still detected in the blood of 2 of 100 young Austrians tested, and testing the specific lotion and perfume one of them used did not find musk ambrette in the product itself, so the source of the banned chemical could not be pinned down.
Weak evidence.
Caveats
N=2; the tested products were negative for musk ambrette, so contamination, an unlisted supply-chain source, or a different untested product cannot be distinguished; no source identified.
Source: Hutter 2009, Science of the Total Environment Link to this fact
Laws and loopholes / Review of other studies
A leading pediatric environmental-health review states that fewer than 20% of the roughly 3,000 high-production-volume industrial chemicals in the US have been tested for potential to cause developmental neurotoxicity.
Weak evidence.
Caveats
Landrigan 2010 attributes this figure to Goldman 1998 (Environ Health Perspect), now read directly in this evidence base (src-1998-chemicals-childrens-environment-risks): Goldman 1998 contains no '20%' statistic and no developmental-neurotoxicity-specific testing figure. Its actual EDF-sourced figures (71% no basic toxicity data at all, 63% not tested for carcinogenicity, <50% tested for any chronic toxicity) describe different, broader endpoints. The citation does not support the specific number or endpoint claimed.
Source: Landrigan 2010, Current Opinion in Pediatrics Link to this fact
Laws and loopholes / Government agency
Allergy UK's product-endorsement page does not disclose who pays for testing or endorsement; it sits under a business-facing URL and ends in a manufacturer submission form, consistent with (but not confirmation of) a manufacturer-initiated, fee-based process.
Weak evidence: Fee/payer structure is inferred from page layout, not stated by the source; do not cite this page for a fee claim.
Source: Allergy UK 2026 Link to this fact
Laws and loopholes / Review of other studies
No law requires manufacturers of scented candles to prove the safety of their products before releasing them onto the market in the US or EU, per the authors.
Weak evidence: General regulatory claim by the review authors, not independently verified against current statute text in this ingest.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Information, not medical advice. See also: myths we won’t tell you.