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 / Measured in people or real products
If you have a confirmed (not just borderline) positive patch test to limonene hydroperoxides, avoiding products with appreciable oxidized/aged limonene is well supported: realistic product-level doses reliably triggered a reaction in this group.
Moderate evidence: Applies to confirmed reactors; a borderline patch-test result is much weaker evidence of true allergy.
What you can do / Measured in people or real products
If you have known fragrance allergy, ask your pharmacist or read the full leaflet (not just the outer box) for topical medicines, and request fragrance-free formulations for wound care, NSAID gels, and antiseptics where alternatives exist; if a topical medicine causes a rash, ask for patch testing with the actual product and its individual ingredients, not just the standard fragrance mix.
Moderate evidence: Practical advice drawn from a single clinic's experience; a negative fragrance-mix patch test does not rule out fragrance allergy from a specific product.
What you can do / Measured in people or real products
In a study of 25 UK homes, easy-to-check building factors (home age, size, number of occupants, single- vs double-glazing) showed no measurable relationship to indoor scent-chemical levels; the homes with the highest levels were those whose occupants reported heavy cleaning/fragrance-product use.
Moderate evidence.
Caveats
Glazing comparison used t-tests on 19 homes with no ventilation-rate data; product-use link is a qualitative activity-log correlation, not a controlled experiment A larger same-lab study (Heeley-Hill 2021, 60 UK homes, daily diaries; Givaudan-funded fieldwork) found cumulative product-use frequency had almost no predictive power for measured VOC levels (R²<0.001), so treat the product-use link as suggestive.
Source: Wang 2017, Environmental Science: Processes & Impacts Link to this fact
What you can do / Self-reported survey
During pregnancy, prefer pouring or wiping cleaning products rather than spraying them, and limit solvent and air-freshener use, since spray application was the exposure most consistently linked to infant respiratory symptoms across this and sibling cohort studies.
Moderate evidence.
Caveats
Based on an observational association, not a controlled trial; the authors' own explanation (spraying increases inhaled dose of both volatile and non-volatile components) is plausible but unproven.
Source: Casas 2013, International Journal of Public Health Industry-funded Link to this fact
What you can do / Self-reported survey
More than a third of people surveyed (37%) report avoiding at least one leave-on scented product (perfume, deodorant, skin cream) because it has caused them skin problems.
Moderate evidence.
Caveats
Self-reported avoidance, not a clinical diagnosis; nearly identical rates in the full interviewed sample (12,377) and the smaller patch-tested subsample (3,119), supporting representativeness.
Source: Diepgen 2015 (EDEN), British Journal of Dermatology Industry-funded Link to this fact
What you can do / Measured in people or real products
People with chronic, treatment-resistant hand eczema and a history of reacting to scented products can ask their dermatologist for patch testing beyond the standard fragrance mix, including citral, Lyral, hydroxycitronellal, and oxidized limonene/linalool.
Moderate evidence: Based on one clinical population's reaction pattern (Heydorn 2003); a dermatologist should tailor markers to local product exposure.
Source: Heydorn 2003, Contact Dermatitis Industry-funded Link to this fact
What you can do / Measured in people or real products
Because galaxolide (HHCB) levels in milk tracked perfume use and tonalide (AHTN) levels tracked scented-laundry-detergent use specifically, choosing fragrance-free perfume and fragrance-free laundry detergent during pregnancy and breastfeeding are each independently plausible ways to lower the corresponding musk chemical passed to a nursing infant.
Moderate evidence.
Caveats
Correlational and cross-sectional, no before/after intervention trial; musk xylene (a nitro musk) showed no association with any product category tested, so this action would not address that compound.
Source: Lignell 2008, Environmental Science & Technology Link to this fact
What you can do / Measured in people or real products
For parents of infants, diaper cream is an under-recognized DEP source that deserves attention alongside fragranced products, not instead of them.
Moderate evidence: Based on a Canadian exposure model with non-Canada-specific use-pattern inputs, not measured infant biomarkers.
Source: Koniecki 2011, Environmental Research Link to this fact
What you can do / Measured in people or real products
A direct chemical test of real fragrance products found no build-up of the allergenic breakdown product (linalool hydroperoxide) even after 9 months of worst-case accelerated aging, so for fine fragrances and antiperspirants specifically, letting a bottle sit open for months to years did not measurably increase this particular hazard.
Moderate evidence.
Caveats
Covers only fine fragrance and antiperspirant formulations tested by one industry lab; does not cover creams, lotions, or other product categories, and does not test whether the general advice to discard old products reduces dermatitis.
Source: Kern 2014, Analytical and Bioanalytical Chemistry Industry-funded Link to this fact
What you can do / Measured in people or real products
Clinicians managing irritable larynx syndrome most often treat reflux (medication and lifestyle measures) and provide voice/relaxation therapy; formal psychotherapy and botulinum toxin injections are used less often, and botulinum toxin appeared less effective than in focal laryngeal dystonia.
Moderate evidence.
Caveats
Descriptive treatment-given data from one clinic, not a controlled efficacy comparison; 2 of 5 laryngospasm patients given botulinum toxin ultimately required tracheotomy, but n is too small to attribute this to the treatment.
What you can do / Self-reported survey
If you are allergic to a fragrance or preservative chemical, reading cosmetic ingredient labels is genuinely difficult, not just for you: in one clinical survey, 46% of patch-test-confirmed allergic patients found it difficult or extremely difficult, and this was significantly worse for people with less education.
Moderate evidence: Single-country (Danish), 3-clinic, self-rated VAS survey of 382 patients; not replicated elsewhere, so per our grading rule it stays below strong.
What you can do / Self-reported survey
People allergic to formaldehyde or methyldibromo glutaronitrile (MDBGN) have an especially hard time reading ingredient labels, likely due to long chemical names and formaldehyde's many synonyms and releasers; ask a dermatologist to write down or print the specific names and synonyms to watch for.
Moderate evidence: Single Danish survey; the mechanism (long/unfamiliar names) is the authors' plausible explanation, not directly tested.
What you can do / Self-reported survey
Many allergic patients who read ingredient labels still don't fully trust them: in one study only about half of patients affirmatively agreed that ingredient labels are accurate, so persistent reactions despite careful label reading are not necessarily a reading mistake.
Moderate evidence: Self-reported trust, not a test of actual label accuracy; the study does not adjudicate whether distrust reflects real label errors or post-hoc reasoning from continued reactions.
What you can do / Self-reported survey
Difficulty reading ingredient labels is a general problem across contact-allergic patients, not one limited to people with several different allergies, so simplifying label-reading advice would help broadly rather than only a small multi-allergic subgroup.
Moderate evidence: Single Danish survey (n=382); multiple-allergy status was defined only across the study's 7 target allergens.
What you can do / Measured in people or real products
A fading chemical smell is not a sign that exposure or irritation has stopped: PGME-exposed subjects lost the ability to smell the compound after about 3 hours at 250 ppm, while eye and nose irritation continued or worsened in those who stayed in the chamber.
Moderate evidence: Demonstrated only for PGME vapor at occupational-accident-level concentrations (hundreds of ppm), not for consumer-level scented product exposure.
Source: Stewart 1970 (Arch Environ Health), Archives of Environmental Health: An International Journal Industry-funded Link to this fact
What you can do / Measured in people or real products
Switching from a fragranced to a fragrance-free laundry detergent cut the fragrance chemical D-limonene coming out of the dryer vent by up to 99.7% (mean 79.1%) within one month, in real households, with no extra cost or apparent inconvenience.
Moderate evidence.
Caveats
4 households switched, D-limonene only; one household's no-product baseline (machine run with no detergent) actually rose 70.3% after the switch, which the paper attributes to residual fragrance chemicals left in the machine or clothing; no statistical testing.
Source: Goodman 2019, Air Quality, Atmosphere & Health Link to this fact
What you can do / Measured in people or real products
Emptying a dryer's lint filter dry (by hand, vacuum, or brush) instead of rinsing it under a tap appears to substantially cut how much textile microfiber ends up in wastewater; a modeled comparison in one study found roughly 12.6 times more fiber reaching water when the filter was rinsed than when the fluff was thrown in household trash.
Moderate evidence.
Caveats
This is the study's own arithmetic model combining its drying data with a prior washing-machine dataset from the same lab, not an independent before/after trial of the two disposal methods; single detergent and appliance models.
Source: Cummins 2023, PLOS ONE Industry-funded Link to this fact
What you can do / Other evidence
Treat a strong, persistent solvent-type smell (heavy cleaning, fresh paint, new furnishings in a poorly ventilated space) as a plausible trigger for eye, nose, throat, or mild respiratory irritation, and ventilate or leave the area if symptoms appear.
Moderate evidence: The doses tested were far higher than most ventilated homes reach; this advice is about avoiding irritant symptoms, not about a demonstrated injury risk from ordinary indoor air.
Source: Pappas et al. 2000, Int J Occup Environ Health 6:1-8 Link to this fact
What you can do / Measured in people or real products
People with a dermatitis distributed under clothing who suspect laundry detergent can ask a dermatologist for patch testing with a 0.1% aqueous dilution of their own detergent (low enough to avoid most irritant false positives), but a single positive reaction needs further dose-response and use-testing to separate true allergy from irritation.
Moderate evidence: Based on one study's protocol; not an independently validated clinical guideline.
Source: Belsito et al. 2002, Journal of the American Academy of Dermatology Industry-funded Link to this fact
What you can do / Test-chamber measurement
Reducing indoor ozone (for example, by filtering incoming air or limiting fresh-air intake on high-outdoor-ozone days) and avoiding heavy simultaneous use of terpene-scented products can reduce the formation of formaldehyde and fine secondary particles indoors, since both the ozone and the fragrance terpene are needed together to generate these byproducts.
Moderate evidence.
Caveats
Derived from a controlled chamber demonstration of the reaction, not from a real-world intervention trial measuring whether these specific mitigation steps lower home concentrations.
Source: Fan et al. 2003, Environmental Science & Technology Link to this fact
What you can do / Self-reported survey
Reducing overall frequent use of chemical household products (disinfectants, bleach, aerosols, air fresheners, and similar) during pregnancy, rather than switching to any one particular product believed to be safer, is the action this study's findings point to.
Moderate evidence.
Caveats
This is an inference from the dose-response composite-score finding and the null single-product-removal analysis, not a tested intervention; the study did not test whether reducing product use lowers a child's wheeze risk.
What you can do / Review of other studies
Never mix chlorine bleach with ammonia or acidic cleaning products, since this releases chlorine gas or trichloramine, both strong respiratory and eye irritants documented to cause acute lung injury in cleaners and housewives.
Moderate evidence: Drawn from background literature the authors cite (occupational case reports and reviews), not from new data collected in this study.
Source: Nickmilder, Carbonnelle & Bernard 2007, Pediatric Allergy and Immunology Link to this fact
What you can do / Self-reported survey
Preferring non-spray (liquid or wipe-application) formats for glass cleaners, furniture polish, and air fresheners is a reasonable precaution, since these three spray product types had the clearest, statistically significant links to new-onset adult asthma in a large multinational cohort study.
Moderate evidence: Based on one observational cohort; not a controlled intervention trial showing that switching formats reduces asthma risk.
Source: Zock et al. 2007, American Journal of Respiratory and Critical Care Medicine Link to this fact
What you can do / Measured in people or real products
Reducing indoor ozone — for example by avoiding ozone-generating 'air purifiers' and ionizers, and by filtering or reducing infiltration of outdoor ozone — reduces both this skin-oil oxidation chemistry and the related chemistry between ozone and fragrance terpenes at the same time, since both start with the same pollutant.
Moderate evidence.
Caveats
Based on the mechanism demonstrated in this paper (ozone as the common trigger), not a direct before/after intervention trial measuring exposure reduction from a specific consumer action.
Source: Wisthaler & Weschler 2010, Proceedings of the National Academy of Sciences Link to this fact
What you can do / Measured in people or real products
If you suspect a deodorant is causing your skin allergy (especially if you are male), ask that patch testing specifically include fragrance mix II and HICC, since the standard fragrance mix I marker is a weaker predictor of deodorant-driven fragrance allergy.
Moderate evidence: Advice extrapolated from a correlational clinic dataset, not from an interventional study testing whether this actually improves diagnosis.
Source: Heisterberg 2011, Contact Dermatitis Link to this fact
What you can do / Measured in people or real products
Read the ingredient list for the named allergens rather than trusting marketing words like 'sensitive' or 'soft' on a deodorant label; in one German sample, products carrying such words were no less likely to contain perfume or a strong allergen than the market as a whole.
Moderate evidence: Single-country label survey; does not establish the words are misleading everywhere, only in this sample.
Source: Klaschka 2012, International Journal of Hygiene and Environmental Health Link to this fact
What you can do / Other evidence
Patients on long-term BAK-preserved glaucoma drops who have ocular surface disease symptoms can ask their ophthalmologist about preservative-free or alternative-preservative (SofZia, Polyquad, or Purite) formulations, which trials show have equivalent intraocular-pressure-lowering efficacy to BAK-preserved drugs.
Moderate evidence.
Caveats
Ocular surface disease symptom improvement with alternative preservatives is mixed across trials and can take 12 or more weeks to appear; benefit is clearest in patients with pre-existing ocular surface disease or long BAK exposure history.
Source: Rasmussen et al. 2014, Journal of Ocular Pharmacology and Therapeutics Industry-funded Link to this fact
What you can do / Measured in people or real products
If you have unexplained or recurring eczema, especially on the hands or face, ask your dermatologist about patch testing that includes oxidized limonene and oxidized linalool, not just the standard fragrance mixes; these two allergens alone accounted for 8% of positive reactions in one large clinic-referred study.
Moderate evidence: Advice extrapolated from a dermatitis-clinic population to the general public; the fraction of the public who would benefit from this specific test addition is not established.
Source: Deza 2016, Contact Dermatitis Industry-funded Link to this fact
What you can do / Review of other studies
Preservative-free (benzalkonium-chloride-free) unit-dose albuterol vials exist and are recommended by this review's authors as an alternative to the benzalkonium-chloride-containing multidose dropper bottle for preparing continuous nebulized albuterol.
Moderate evidence.
Caveats
This is an authors' clinical recommendation based on the weight of mechanistic and threshold-dose evidence, not the result of a controlled outcome trial comparing the two formulations.
Source: Prabhakaran 2017 Link to this fact
What you can do / Self-reported survey
Only 5% of nurses in this study reported using a face mask or respirator when handling disinfectants, and use was more common among nurses with worse asthma control (likely because symptomatic nurses sought protection, not because protection failed); the authors explicitly recommend prioritizing elimination or substitution (e.g., non-chemical disinfection methods such as steam or UV light) over personal protective equipment as the more effective prevention strategy.
Moderate evidence.
Caveats
Because so few nurses used respiratory protection, the study was underpowered to test whether it actually modified the disinfectant-asthma-control association (P-interaction >=0.40, not significant either way).
Source: Dumas 2017, European Respiratory Journal Link to this fact
What you can do / Measured in people or real products
Choosing an unscented candle over a scented one made from the same wax measurably lowers the release of combustion pollutants (VOCs, PAHs, formaldehyde), based on this chamber study, though unscented candles still produce carbon dioxide, carbon monoxide, nitrogen oxides, and ultrafine particles from ordinary combustion.
Moderate evidence: Demonstrated for purpose-built research candles across 4 wax types and 5 fragrance families, not verified for any specific retail candle brand.
Source: Salthammer 2021, Environment International Industry-funded Link to this fact
What you can do / Measured in people or real products
Ultrafine particle release from a burning candle is highest in the first 30-60 minutes after lighting, on average 3 to 5 times higher than during steady burning, so ventilating a room in the first hour after lighting candles removes more particles than ventilating later in a burn.
Moderate evidence.
Caveats
Comparison is described qualitatively in the text ("on average a factor of 3-5 higher"), not given as a precise table value; based on the ignition-phase behavior of the chamber's continuous particle monitor, not a home-scale test.
Source: Salthammer 2021, Environment International Industry-funded Link to this fact
What you can do / Review of other studies
People who use BAK-preserved eye drops long-term (especially multiple glaucoma medications) and notice stinging, dryness, redness, or blurred vision can ask their eye doctor whether an alternative-preservative, preservative-free, or sustained-release option is available, since several studies cited in this review found comparable eye-pressure control with less surface toxicity.
Moderate evidence.
Caveats
Based on a company-funded review citing multiple smaller clinical studies, not an independent meta-analysis; preservative-free and sustained-release options are typically more expensive and not always well covered by insurance.
Source: Goldstein 2022, Eye Industry-funded Link to this fact
What you can do / Other evidence
Placing a reed diffuser closer to where you sleep (a bedside cupboard) rather than farther away (a dresser) raised the modeled chemical level in the breathing zone by about 38% after a week.
Moderate evidence: Modeled, not directly measured in an occupied room; specific to this product's emission rate and this bedroom geometry.
Source: Zhang 2024, Cell Reports Physical Science Link to this fact
What you can do / Other evidence
Doubling a room's air exchange rate (more ventilation) cut the modeled breathing-zone reed-diffuser chemical concentration to about 60% of the low-ventilation level.
Moderate evidence: Modeled, not directly measured; China-specific ventilation-rate assumptions.
Source: Zhang 2024, Cell Reports Physical Science Link to this fact
What you can do / Test-chamber measurement
More fiber sticks in a reed diffuser sharply raise the chemicals it releases: modeling showed one stick could raise the indoor chemical level roughly 9- to 11-fold, and two sticks roughly 19- to 24-fold, compared to the bottle alone.
Moderate evidence: Modeled from one product's fitted transport parameters; relative multiplier, not an absolute health-relevant dose.
Source: Zhang 2024, Cell Reports Physical Science Link to this fact
What you can do / Measured in people or real products
A portable HEPA air cleaner run continuously on a quiet fan setting cut median fine-particle (PM2.5) pollution by about 79% and coarser particles (PM10) by about 64% in the room where it sat, measured over 24 hours in 26 real homes.
Moderate evidence: Real-world randomized cross-over trial, but n=26 homes and a single 24-hour intervention window; publicly funded, no industry involvement.
Source: Lu 2024, Aerosol and Air Quality Research Link to this fact
What you can do / Measured in people or real products
Homes with central forced-air heating or air conditioning running got more consistently significant particle reductions from the same portable air cleaner, including in the adjoining room during the day, than homes without central air in use.
Moderate evidence.
Caveats
The between-group comparison of effectiveness values (CAH vs no CAH) itself was not statistically significant (Mann-Whitney U, p>0.05); the CAH effect shows up as more reliable/significant reductions, not necessarily a larger point estimate.
Source: Lu 2024, Aerosol and Air Quality Research Link to this fact
What you can do / Measured in people or real products
Increasing outdoor air ventilation (from about 3 to 6.5 air changes per hour) reduced the amount of larger (3-100 nm) particles that built up during scented wax melt use, but did not stop the initial burst of the smallest (sub-3 nm) particles from forming.
Moderate evidence.
Caveats
Two ventilation rates tested in one test house; the smallest-particle (nanocluster) burst was not eliminated by the higher ventilation rate tested, so ventilation alone is a partial, not complete, mitigation.
Source: Patra et al. 2025, Environmental Science & Technology Letters Link to this fact
What you can do / Measured in people or real products
Fabric type changes how much added perfume stays on clothes after washing: in a lab wash simulator, polyester retained more of a technical perfume accord than cotton after a full wash-and-rinse cycle, because cotton lost an average of about 70% of the perfume it picked up during the main wash over three rinses, versus only 40%-50% for polyester.
Moderate evidence.
Caveats
Industry (Procter & Gamble) lab study; coi/industry-funded despite the paper's own 'no conflict of interest' statement. Used a small-scale bench wash simulator, a model detergent, and a synthetic 22-component technical perfume accord, not a named commercial detergent or perfume. Measured fabric immediately after washing/rinsing only, not after days of storage or wear.
Source: Marcotullio 2025, Journal of Surfactants and Detergents Industry-funded Link to this fact
What you can do / Measured in people or real products
Washing cotton in cold water (20C) can deposit MORE, not less, of the more water-soluble perfume ingredients onto the fabric than a warmer 40C wash, because colder water pushes more hydrophilic perfume into surfactant micelles that then break and redeposit during rinsing; this effect was specific to cotton with detergent present and did not occur on polyester or on cotton without surfactant.
Moderate evidence: Coi/industry-funded (Procter & Gamble); one lab bench simulator, one detergent formula, one synthetic perfume accord; not tested on a named commercial cold-wash detergent.
Source: Marcotullio 2025, Journal of Surfactants and Detergents Industry-funded 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 / Measured in people or real products
If a deodorant use test on the forearm is negative but you still suspect that deodorant is causing your armpit rash, ask a clinician to repeat the test directly in the armpit.
Moderate evidence: Based on a single 1998 study of 12 informative deodorants; two-thirds of confirmed reactions were detected only in the axilla, never on the standard forearm test site.
Source: Johansen et al. 1998, Contact Dermatitis Link to this fact
What you can do / Measured in people or real products
In this 1996 sample, 3 of 73 deodorants labeled "not perfumed" genuinely contained none of the 21 fragrance substances tested, on chemical analysis.
Moderate evidence: Very small sample (n=3) from one country/year snapshot; does not establish that "not perfumed"/"fragrance-free" labels are reliable in general or in other markets/years.
Source: Rastogi et al. 1998, Contact Dermatitis Link to this fact
What you can do / Measured in people or real products
If you have armpit rashes and suspect your deodorant, ask your dermatologist for patch testing that includes hydroxycitronellal specifically rather than relying on a Fragrance Mix I result alone, since a positive fragrance-mix reaction does not identify which of its 8 constituents is responsible.
Moderate evidence: Extrapolated consumer advice from a clinical elicitation study; not itself a tested intervention.
Source: Svedman et al. 2003, Contact Dermatitis Link to this fact
What you can do / Other evidence
If you have unexplained facial or hand eczema and a history of reacting to a scented deodorant or cologne, ask your dermatologist about patch testing with your own stay-on cosmetic products plus HICC (Lyral), not just the standard fragrance mix.
Moderate evidence: Risk-factor odds ratios come from one case-referent study cited by the review, not replicated here.
Source: Johansen 2003, Am J Clin Dermatol 4(11):789-798, American Journal of Clinical Dermatology Link to this fact
What you can do / Measured in people or real products
Most positive reactions (7 of 10, 70%) did not appear until after 2 weeks of twice-daily deodorant use, so a short 1-2 week trial of a new product is not a reliable way to rule out a delayed fragrance allergy.
Moderate evidence: Based on 10 reactors in a single study; the authors recommend use tests run at least 4-6 weeks for this reason.
Source: Bruze et al. 2005, Contact Dermatitis Link to this fact
What you can do / Review of other studies
Patch testing a patient's own perfume, deodorant, or shaving lotion, not only a standardized fragrance panel, has detected sensitizations (e.g. to jasmine absolute, ylang ylang oil, lyral) that the panel alone missed.
Moderate evidence.
Caveats
Relayed from North American (Belsito 2006) and German IVDK (Uter 2007) clinical series; useful practical guidance for allergic patients even though Brasch's own account is secondary.
Source: Brasch 2007, Current Opinion in Allergy and Clinical Immunology Link to this fact
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 / Other evidence
If avoiding D5/cyclosiloxanes, checking ingredient labels matters most for antiperspirants and leave-on hair serums/styling products, where D5 concentrations are typically highest.
Moderate evidence: Product-concentration figures are from a cited survey (Wang et al., 2009), not measured in this paper.
Source: Montemayor 2013, Chemosphere Industry-funded Link to this fact
What you can do / Measured in people or real products
Checking a cosmetic product's full ingredient list for the 26 EU-named fragrance allergens catches allergens that the generic words 'parfum', 'fragrance' or 'aroma' alone would miss: in this study, almost 1 in 17 fragranced products (5.9%) named a specific allergen without using any of those generic words at all.
Moderate evidence.
Caveats
Applies to the EU, where the 26 allergens must be individually named above threshold; label-reading cannot catch allergens used below the labeling threshold or fragrance chemicals outside the list of 26.
Source: Bennike 2017/2018 Link to this fact
What you can do / Review of other studies
If you suspect fragrance allergy, ask your dermatologist to test a dedicated fragrance series, not just the standard baseline patch-test panel, including limonene and linalool hydroperoxides and your own personal products, since the baseline markers alone miss a large share of fragrance allergy cases.
Moderate evidence: Expert-opinion clinical recommendation from a review author, not a trial comparing diagnostic strategies.
Source: de Groot 2020, Dermatitis 31(1):13-35, Dermatitis® Link to this fact
What you can do / Review of other studies
People who suspect a fragrance allergy should choose products specifically labeled "fragrance free" rather than "hypoallergenic" or "unscented," since the latter two terms may still permit some fragrance in the product.
Moderate evidence.
Caveats
Practice advice relayed from prior clinical literature already in this evidence base (see src-2007-benzyl-alcohol-covert-fragrance, src-2024-whiff-of-trouble-allergic-contact-dermatitis-fragrance); US labeling terms are not legally standardized.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
What you can do / Review of other studies
If a standard allergy patch-test panel is negative but a fragrance or contact allergy is still suspected, ask about extended/reflex testing with fragrance mixture II, balsam of Tolu, lichen acid mix, hydroperoxides of limonene and linalool, and (for suspected aluminum allergy) 10% aluminum chloride hexahydrate.
Moderate evidence.
Caveats
A US clinical-practice recommendation; the register records disagreement between expert groups over whether oxidized limonene/linalool preparations over-call weak reactions as true allergy.
Source: Musicante 2024, Cutis Industry-funded Link to this fact
What you can do / Animal study
If burning scented candles indoors, ventilate the room (open window or extraction) rather than burning in a sealed, air-conditioned space, and prefer shorter burn times: in this study the worst inflammatory and histopathological outcomes came from the longest daily exposure (6 h/day) in a fully sealed room.
Moderate evidence: Inferred from a rat model with an unmeasured indoor dose; the specific ventilation rate needed to meaningfully reduce exposure was not tested.
Source: Mohamed et al. 2025, Frontiers in Public Health Link to this fact
What you can do / Measured in people or real products
Run the kitchen exhaust hood during and for a while after cooking, especially when morning sunlight reaches the kitchen: secondary aldehyde formation can keep rising for a period after the stove is off, so shutting the hood off right when cooking ends may miss a later pollution peak.
Moderate evidence: Based on one real-world kitchen and two contrasting days; effect size in other kitchens/climates untested.
Source: Deng 2026, Environment International Link to this fact
What you can do / Measured in people or real products
Ventilate well during and after burning incense, particularly in small or poorly ventilated rooms (including temples and shrines), given this study's isocyanate and nitrogen-heterocycle findings.
Moderate evidence: Based on one incense brand and one room size; personal exposure during typical incense use was not measured, only room-average concentrations.
Source: Deng 2026, Environment International Link to this fact
What you can do / Measured in people or real products
Because diethyl phthalate (DEP) was found in essentially all fragranced cosmetic products FDA tested (5 of 5 in 2006, 11 of 11 in 2010) but is never named on the label when added via 'fragrance,' choosing unscented or fragrance-free products is a more reliable way to avoid it than reading a fragranced product's ingredient list.
Moderate evidence: Based on FDA's own two product-content surveys, not a study of consumer avoidance behavior or of what ingredients replace DEP in reformulated products.
Source: Hubinger 2010, Journal of Cosmetic Science Link to this fact
What you can do / Review of other studies
Regulatory bodies (France's Afssaps, Norway's VKM) advise against applying antiperspirant to broken or freshly shaved skin because aluminum skin penetration rises substantially when the skin barrier is compromised.
Moderate evidence: Precautionary regulatory advice, not a demonstrated health outcome from following or not following it.
Source: Martini 2020, Annales de Dermatologie et de Vénéréologie Link to this fact
What you can do / Measured in people or real products
Because hormone-disrupting chemicals cluster by product type, cleaners, synthetic detergents, fabric softeners, air fresheners, and deodorants are the household product categories where checking for isothiazolinone preservatives (such as benzisothiazolinone) and fragrance chemicals (such as hexyl cinnamaldehyde, geraniol, and citronellol) is likely to be most worthwhile.
Moderate evidence: Reflects which chemicals are most often listed in this product database, not which products emit the most or pose the greatest measured exposure.
Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact
Information, not medical advice. See also: myths we won’t tell you.