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 / 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
What you can do / Advocacy group testing
This report recommends free consumer apps (Yuka, Tox Fox, Kemiluppen) and trusted ecolabels (Nordic Swan, EU Ecolabel) or fragrance-free certification labels (Asthma Allergy Denmark, Allergy Certified) as ways to identify or avoid suspected EDCs and allergens in personal care products.
Weak evidence: The report does not test whether using these apps or labels measurably reduces a person's chemical exposure or biomarkers.
Source: Tegengif 2022 Link to this fact
What you can do / Self-reported survey
Keeping scented-candle sessions shorter (well under 60 minutes) may reduce symptom risk somewhat, since the longest-duration group (>60 min per session) showed the largest (though not statistically significant) increases in headache, sneezing, and wheezing odds.
Weak evidence.
Caveats
Rests on one small, non-representative, single cross-sectional survey; none of the duration-based odds ratios reached statistical significance (all 95% CIs crossed 1), so this is a plausible precaution, not an established dose threshold.
Source: Al Khathlan et al. 2023, BMC Public Health Link to this fact
What you can do / Lab study (cells or chemistry)
Cold-atmospheric-plasma deodorizing devices are an emerging non-chemical, non-fragrance approach to underarm odor control worth watching as an alternative to conventional antimicrobial/fragranced antiperspirants.
Weak evidence.
Caveats
Based on one prototype tested only against cultured bacteria and porcine skin dosed with synthetic odor compounds; no human trial, no skin-safety or allergy testing, and the device generates ozone (a known respiratory irritant) as part of its mechanism.
Source: Bok et al. 2024, Scientific Reports Link to this fact
What you can do / Other evidence
Airing out a room after burning scented candles helps remove residual chemical compounds produced during burning.
Weak evidence: Common-sense ventilation advice; not independently quantified in this editorial or checked against primary ventilation-effect data in this evidence base.
Source: Nazir et al. 2024, Annals of Medicine & Surgery Link to this fact
What you can do / Other evidence
People should use scented candles with caution in closed spaces and should refrain from using them around vulnerable groups such as pregnant women, children, the elderly, and people with pre-existing cardiopulmonary conditions.
Weak evidence: A precautionary recommendation, not based on a candle-specific dose-response or exposure-outcome study in any of the named vulnerable groups.
Source: Singh 2023, Environmental Science & Technology Link to this fact
What you can do / Other evidence
A structured home walkthrough that identifies and removes common VOC sources (mothballs, scented cleaning and personal-care products, candles, garage-stored chemicals) and separates stored chemicals from living space (e.g., moving gasoline/solvents/paints to detached storage) reduced measured indoor VOC levels in the homes studied.
Weak evidence.
Caveats
Professional testing and a trained team delivered this intervention over 5 visits across a year; the paper does not test which individual component (removal vs. substitution vs. new storage vs. counseling) drove the VOC reduction. Evidence is one small uncontrolled case series.
Source: Rincón et al. 2024, Primary Health Care Research & Development Link to this fact
What you can do / Review of other studies
Because diet is the main route of human exposure to BPA and phthalates from food packaging, avoiding microwaving food in plastic, cutting back on canned food, and choosing glass, stainless-steel, or aluminum containers instead of plastic can reduce dietary exposure to these obesogenic chemicals.
Weak evidence.
Caveats
This reduces measured chemical exposure; no trial has tested whether making this switch actually changes body weight or obesity risk in people. The review infers this from exposure routes; it cites no intervention study measuring the reduction.
Source: Dalamaga 2024, International Journal of Molecular Sciences Link to this fact
What you can do / Review of other studies
At least 25% (and likely closer to 50%) of the sunscreen applied to skin washes off during sea bathing, and an estimated 35+ kg of sunscreen is deposited per day for every 1,000 people visiting a single beach, so choosing physical sun protection (clothing, hats, shade) over reapplying sunscreen right before swimming directly reduces this wash-off pathway into marine water.
Weak evidence.
Caveats
Wash-off fraction estimates vary between the cited studies (25% vs approx. 50%); the beach-deposition figure is a modeled estimate, not a direct field measurement of ecological harm This action is the ingest's inference from a review's cited wash-off and modeled deposition figures; no study tested it.
Source: Hodge 2025, Marine Pollution Bulletin Link to this fact
What you can do / Review of other studies
The study's authors argue that reducing DEHP/plastic-related cardiovascular mortality requires regulation (banning or restricting DEHP in products, improving labeling), better waste management, and international cooperation such as the UN's Global Plastics Treaty negotiations, rather than relying on individual consumer avoidance alone.
Weak evidence: This is the authors' policy recommendation; no intervention was tested in this study.
What you can do / Government agency
A patient with fragrance/chemical sensitivity asking a clinic to have staff avoid fragrance for one scheduled appointment is asking for something narrower than a facility-wide rule, and DOJ's 1995 'usually not reasonable' answer was addressed to the broader framing, not this narrower one.
Weak evidence: DOJ never separately analyzed the narrower, one-appointment request; this is an inference from reading the letter against its own attached correspondence, not a DOJ holding.
Source: DOJ TAL605, 1995 Link to this fact
What you can do / Self-reported survey
Perfume is most often sprayed on the neck and throat, then the arms — close to the nose and mouth — so people concerned about fragrance inhalation might consider applying it lower on the body or on clothing instead.
Weak evidence: Based on where 326-340 already-regular perfume users in one US industry survey said they applied product, not on any measurement of how application site changes inhaled dose.
Source: Loretz 2006, Food and Chemical Toxicology Industry-funded Link to this fact
What you can do / Measured in people or real products
A typical day's use is about 4 g for facial cleanser, about 14 g (median 10.6 g) for hair conditioner, and about 0.04 g for powder eye shadow, based on a two-week diary-and-weighed-container study of nearly 300 regular US users of each product using their own regular brand.
Weak evidence.
Caveats
Rests on this single 2008 industry study of women-only, US-only, already-regular users of that specific product category; amounts are ratio estimates from total container weight change over two weeks, not measured per application.
Source: Loretz 2008, Food and Chemical Toxicology Industry-funded Link to this fact
What you can do / Self-reported survey
Women with longer, thicker, or curlier hair used noticeably more hair conditioner overall than women with short, fine, or straight hair, while hair oiliness, dryness/damage, and color treatment showed no clear effect on the amount used.
Weak evidence: Rests on this single 2008 industry study's self-reported hair-characteristic categories (box-plot comparison), not a controlled or dose-response analysis.
Source: Loretz 2008, Food and Chemical Toxicology Industry-funded Link to this fact
What you can do / Government agency
Frozen and fatty packaged foods in printed cartonboard (frozen foods, jellies, savory snacks, high-fat items like chocolate) were the categories a UK FSA survey found most likely to carry benzophenone residue from printing-ink migration; fresh or non-printed-packaging foods are a lower-exposure alternative for anyone wanting to reduce incidental dietary intake.
Weak evidence.
Caveats
Based on one national survey's positive-detection rates by food category, not a dose-response health-outcome study Graded weak: what-you-can-do resting on one survey relayed through the IARC monograph.
Source: IARC 2013 Link to this fact
What you can do / Review of other studies
The Endocrine Society recommends that regulatory agencies and civil society organizations support consumer-facing programs like the US EPA's Safer Choice and develop educational materials so consumers can identify and adopt safer product alternatives.
Weak evidence.
Caveats
A general recommendation, not a specific list of safer cosmetic or fragrance alternatives; Safer Choice itself is a voluntary EPA labeling program, not a cosmetics-specific standard.
Source: Endocrine Society 2025 Link to this fact
What you can do / Self-reported survey
If you want to try a pleasant scent at bedtime, this one small study suggests a diffuser-style, indirect delivery may feel more pleasant than a nasal clip or pillow spray (pillow spray was linked to worse self-reported sleep), but don't expect it to change your sleep architecture, and there's no data here on whether it's safe to breathe nightly.
Weak evidence: Rests on one small, non-randomized, industry-funded study with a null objective outcome; not replicated.
Source: Li et al. 2025, Scientific Reports Industry-funded Link to this fact
What you can do / Self-reported survey
People pursuing an MCS accommodation in Canada should ask healthcare providers to document functional limitation, not just a diagnosis, and should keep a written record of every accommodation request and outcome, since the legal duty to accommodate turns on function and this study found requests and refusals were often repeated five or more times.
Weak evidence.
Caveats
Drawn from one self-report survey's qualitative themes and the authors' own policy recommendations, not tested as an intervention; rests on a single small, advocacy-recruited study.
Source: Diallo 2026 Link to this fact
What you can do / Measured in people or real products
Before applying moisturizer to an infant's skin, wash hands thoroughly, and give careful consideration to both the frequency and the type of product used, per the study authors' own cautious recommendation.
Weak evidence.
Caveats
This recommendation rests on one observational cohort (plus a matching but non-significant RCT signal from BEEP); it is not established clinical guidance, and moisturizers remain first-line treatment for infants who already have eczema.
Source: Perkin 2021 (EAT cohort), Journal of Allergy and Clinical Immunology Link to this fact
What you can do / Measured in people or real products
Choosing cellulosic-fiber (cotton, viscose) rather than synthetic (nylon, polyester) next-to-skin clothing may reduce how much nonpolar ketone and aldehyde sweat odor is released into the air shortly after exercise, based on one lab study's yarn-bundle sorption/release measurements.
Weak evidence.
Caveats
Rests on one lab study using isolated yarn bundles (not real garments) and a sterile synthetic sweat solution with no bacterial component, which is the actual source of most real-world body odor; not yet tested on worn clothing or replicated by an independent group.
Source: McQueen 2024, Textile Research Journal Link to this fact
What you can do / Measured in people or real products
In laboratory testing on one sunscreen spray, fitting a tapered external tube over the spray-can nozzle reduced the modeled number of submicron particles reaching the respiratory tract by about 89% and the mass reaching it by about 66%, without reducing the amount of product delivered.
Weak evidence.
Caveats
Single chamber study, single lab, one primary test product; only partially cross-checked (one alternate tube geometry) on two other product types; the modification is a research prototype, not available on any commercial product; authors call the work a proof-of-concept.
Source: Dai et al. 2026, ACS Environmental Au Link to this fact
What you can do / Review of other studies
NRDC's 2007 report recommends avoiding air fresheners altogether or, if used, choosing products with the lowest measured phthalate levels and favoring ventilation over added fragrance to address household odors.
Weak evidence: An advocacy organization's risk-averse recommendation, not a demonstrated dose-response health benefit from switching products.
Source: NRDC 2007, Clearing the Air Link to this fact
What you can do / Measured in people or real products
Daily application of a fragrance-free emollient to a newborn with a family history of atopic dermatitis may reduce the baby's risk of developing eczema in the first several months of life, based on this one trial.
Weak evidence.
Caveats
Rests on one single-center trial of one specific product in a high-risk Japanese population; the much larger BEEP RCT (10x the sample, a different emollient) found no eczema-prevention benefit at all, and some evidence of increased skin infections — present both results together, not this one alone.
Source: Horimukai et al. 2014, Journal of Allergy and Clinical Immunology Industry-funded Link to this fact
What you can do / Self-reported survey
Migraineurs who notice perfume, paint/varnish, gasoline, or bleach smells before their attacks may want to keep a trigger diary, since these were the most common self-reported odor triggers in one clinic sample.
Weak evidence.
Caveats
Rests on a single non-random clinic sample (n=200, one Brazilian city, 2011); a personal pattern should be confirmed prospectively, not assumed from one study, and may reflect premonitory-phase symptom misattribution rather than a true external trigger.
What you can do / Self-reported survey
A person who notices odor aversion (or light/sound sensitivity, or food craving) starting hours before a migraine headache can consider it a possible early-warning premonitory symptom of the attack, not necessarily proof that the odor, light, or food caused the attack.
Weak evidence: Based on a retrospective association in one tertiary-care cohort; does not establish that recognizing premonitory symptoms changes outcomes.
Source: Schulte 2015, The Journal of Headache and Pain Link to this fact
What you can do / Self-reported survey
Migraineurs who notice their attacks are triggered by specific odors (most commonly perfume, cleaning products, cigarette smoke, or vehicle exhaust in this sample) may reasonably consider reducing exposure to those specific triggers as a low-cost self-management step.
Weak evidence: Based on self-reported association in one clinical sample, not a controlled-avoidance or provocation trial; benefit of avoidance was not tested.
Source: Fornazieri 2016, Headache: The Journal of Head and Face Pain Link to this fact
What you can do / Measured in people or real products
Parents who want to reduce infant phthalate exposure can limit the number of infant care products used on their baby and avoid applying lotion or powder unless medically indicated.
Weak evidence: This is the study authors' own recommendation, not a tested intervention; it is based on the correlational findings in the same study.
Source: Sathyanarayana et al. 2008, Pediatrics Link to this fact
What you can do / Measured in people or real products
Because this study's own route argument points to prenatal (placental) transfer, not breastfeeding, as the main way synthetic musk fragrance chemicals reach a baby, choosing fragrance-free personal-care and laundry products during pregnancy specifically, not only while breastfeeding, is a plausible way to reduce an infant's earliest musk exposure.
Weak evidence.
Caveats
Inferred from pharmacokinetics (musks' short half-life) and matrix comparisons, not from measured product use or from an intervention study; no study has tested whether reducing a mother's product use lowers her infant's cord-blood or milk musk levels.
What you can do / Measured in people or real products
Because fragrance musk exposure has been linked to personal-care and laundry product use in other studies, choosing fragrance-free cosmetics and laundry products during pregnancy and breastfeeding is a plausible way to reduce a baby's prenatal and infant musk exposure.
Weak evidence.
Caveats
This paper collected no personal-care-product-use data itself; the action is inferred from sibling studies (Hutter 2009, Lignell 2008) that did test product use, not from this paper's own data.
Source: Zhang 2015, International Journal of Hygiene and Environmental Health Link to this fact
What you can do / Measured in people or real products
People who want to reduce systemic absorption of chemical UV filters while FDA's requested toxicology studies remain outstanding can choose mineral sunscreens (zinc oxide or titanium dioxide, the only two actives FDA has found generally recognized as safe and effective) or rely more on sun-protective clothing and shade.
Weak evidence: This is a risk-reduction option, not advice to avoid sun protection; the paper explicitly says its findings do not mean people should stop using sunscreen.
Source: Matta 2020, JAMA Link to this fact
What you can do / Measured in people or real products
This pilot study's biomarker evidence adds modest support to choosing unscented, minimal-ingredient menstrual products generally, consistent with the stronger product-content evidence from this group's earlier FHP survey, but does not show a cycle-wide VOC exposure spike during menstruation.
Weak evidence: Based on a small, non-generalizable pilot cohort (n=25, university-affiliated women); not a strong independent basis for action on its own.
Source: Ding 2022, Journal of Women's Health Link to this fact
What you can do / Other evidence
Favoring fragrance-light wash and moisturizer formulations, and avoiding heavy or frequent use, may reduce modeled n-nonane and benzene exposure from feminine hygiene products the most, based on a toxicokinetic model's risk ranking.
Weak evidence: This is a modeled, not measured or tested, recommendation; the same model found most VOCs' total exposure is dominated by indoor air, not product choice.
Source: Lin 2025, Environmental Health Perspectives Link to this fact
Information, not medical advice. See also: myths we won’t tell you.