Don’t take our word for it. Here’s every fact on this site, with its evidence grade, its caveats, and a link to the source, so you can check us.
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.
Laws and loopholes / Other evidence
Color additives that do not need FDA certification may appear on a US food label as just 'Artificial Color', 'Artificial Color Added' or 'Color Added', and colorings in butter, cheese and ice cream need not be listed unless a color regulation requires it (21 CFR 101.22(k)(2)-(3)).
Strong evidence: Certified colors must be named; this describes the non-certified route.
Source: 21 CFR 101.22 (eCFR 2026), Code of Federal Regulations, Title 21, Section 101.22 (eCFR) Link to this fact
Laws and loopholes / Government agency
EFSA's polysorbate exposure estimate counts only food additive uses; it states that exposure from cosmetic ingredients, personal care products, textiles and pharmaceuticals was not considered, and that carrier uses in flavorings, colors and nutrient preparations were also left out.
Strong evidence: Stated limitation in the opinion; no quantification of the omitted sources.
Source: EFSA ANS Panel (2015), full opinion, EFSA Journal Link to this fact
Laws and loopholes / Other evidence
Canada's 2021 MAiD amendment act (S.C. 2021, c. 2, Bill C-7, assented to 2021-03-17) repealed the Criminal Code requirement that a person's natural death be reasonably foreseeable for MAiD eligibility.
Strong evidence: Describes the act as enacted; current law is in the Criminal Code consolidation.
Source: S.C. 2021, c. 2 (Bill C-7), annual statute page Link to this fact
Laws and loopholes / Other evidence
The act created two sets of safeguards, one for people whose natural death is reasonably foreseeable (s. 241.2(3)) and one for those whose natural death is not (s. 241.2(3.1)).
Strong evidence: The act's own headings are 'natural death foreseeable' and 'natural death not foreseeable'; 'Track Two' is a press label.
Source: S.C. 2021, c. 2 (Bill C-7), annual statute page Link to this fact
Laws and loopholes / Other evidence
For a person whose natural death is not reasonably foreseeable, the act requires at least 90 clear days between the start of the first eligibility assessment and the provision of MAiD.
Strong evidence.
Caveats
A shorter period is allowed if both assessors find loss of capacity to consent is imminent and the first practitioner considers it appropriate. Applies to the not-foreseeable set only.
Source: S.C. 2021, c. 2 (Bill C-7), annual statute page Link to this fact
Laws and loopholes / Other evidence
For the not-foreseeable set, the act requires that the person be informed of means to relieve suffering, including counseling, mental health and disability support services, community services and palliative care, and be offered consultations with relevant professionals.
Strong evidence: States a duty on the practitioner to inform and offer; the act does not require that any service be provided or available.
Source: S.C. 2021, c. 2 (Bill C-7), annual statute page Link to this fact
Laws and loopholes / Other evidence
The act required an independent expert review of protocols, guidance and safeguards for MAiD requests by people with a mental illness, reported to the Ministers of Justice and Health within one year of royal assent and tabled in Parliament within 15 sitting days of receipt.
Strong evidence: The act requires the review and report; it does not show whether or when they were completed.
Source: S.C. 2021, c. 2 (Bill C-7), annual statute page Link to this fact
Laws and loopholes / Other evidence
The act's preamble names the Quebec Superior Court decision Truchon v. Attorney General of Canada as something the government committed to respond to, and affirms Canada's obligations under the UN Convention on the Rights of Persons with Disabilities and a human rights-based approach to disability inclusion.
Strong evidence: Preamble statements of purpose; they do not themselves set eligibility rules.
Source: S.C. 2021, c. 2 (Bill C-7), annual statute page Link to this fact
Laws and loopholes / Other evidence
The act lets a person whose natural death is reasonably foreseeable receive MAiD after losing capacity to consent, under a prior written arrangement, unless they show refusal or resistance by words, sounds or gestures.
Strong evidence: Conditions apply; involuntary responses to contact do not count as refusal (3.3).
Source: S.C. 2021, c. 2 (Bill C-7), annual statute page Link to this fact
Laws and loopholes / Other evidence
"Consensus was not achieved among MDRC members about whether Ms. B was eligible for MAiD": many members would not have considered her eligible, while others cautiously saw suitable clinical evidence for eligibility based on MCSS.
Strong evidence: Strong as a statement of what the report says; it records a split, not a ruling. The MAiD practitioners had determined eligibility from medically confirmed MCSS.
Source: Ontario MDRC Report 2024-3 (OCC, 2024; non-official copy) Link to this fact
Laws and loopholes / Other evidence
Most committee members agreed that in the MCSS case the MAiD process "should give way to urgent social services intervention and maximize supportive healthcare options to reduce symptoms and suffering prior to proceeding with MAiD."
Strong evidence: A majority discussion view (members' opinions were not counted), not a binding direction.
Source: Ontario MDRC Report 2024-3 (OCC, 2024; non-official copy) Link to this fact
Laws and loopholes / Other evidence
The committee's review of three Track 2 deaths was not an inquest and not a legal determination: cases were purposively selected to prompt discussion, are not representative of most MAiD deaths, and the report states it "did not aim to establish consensus."
Strong evidence: Quoted framing; the MDRC is an advisory committee separate from the nurse coroner investigators who review every reported MAiD death.
Source: Ontario MDRC Report 2024-3 (OCC, 2024; non-official copy) Link to this fact
Laws and loopholes / Other evidence
In 2023 Ontario recorded 4,644 MAiD provisions, 116 of them Track 2 (non-reasonably foreseeable natural death); Track 2 recipients were more often female (61.2%), more often under 60, and more often lived alone at every age (for example 45.7% vs 28.5% at ages 70-79).
Strong evidence: Provincial reporting data; small Track 2 numbers; the report says the tracks appear to be distinct populations. Fig. 7 values checked against the page image.
Source: Ontario MDRC Report 2024-3 (OCC, 2024; non-official copy) Link to this fact
Laws and loopholes / Government agency
The Canadian Human Rights Commission says the Canadian Human Rights Act protects people with disabilities from discrimination and that this includes people with environmental sensitivities.
Strong evidence: Agency guidance, not a court ruling; applies to federally regulated employers and service providers. Page undated (captured 2026-10-21).
Source: CHRC 2026 web Link to this fact
Laws and loopholes / Government agency
The CHRC says a federally regulated employer or service provider has a legal duty to accommodate workers, contractors, customers and clients with environmental sensitivities up to the point of undue hardship.
Strong evidence: Federal jurisdiction only; the page does not define undue hardship or discuss provincial law.
Source: CHRC 2026 web Link to this fact
Laws and loopholes / Other evidence
Canada's Criminal Code requires at least 90 clear days between the start of the first eligibility assessment and the provision of medical assistance in dying when the person's natural death is not reasonably foreseeable (s. 241.2(3.1)(i)), unless both assessors judge loss of capacity to consent imminent, in which case a shorter period the first practitioner considers appropriate applies.
Strong evidence: Statute text as consolidated to 2026-09-30; later amendments may apply. 'Track Two' is a common label, not statutory wording.
Source: Criminal Code s. 241.2 (consolidation current to 2026-09-30) Link to this fact
Laws and loopholes / Other evidence
When natural death is not reasonably foreseeable, the practitioners must ensure the person has been informed of the means available to relieve their suffering, including where appropriate counseling, mental health and disability support services, community services and palliative care, and has been offered consultations with relevant professionals (s. 241.2(3.1)(g)).
Strong evidence: The duty is to inform and offer consultations, not to provide the services. Consolidation current to 2026-09-30.
Source: Criminal Code s. 241.2 (consolidation current to 2026-09-30) Link to this fact
Laws and loopholes / Other evidence
The statute requires the practitioners to discuss the reasonable and available means of relieving the person's suffering with the person and to agree with the person that they have given those means serious consideration (s. 241.2(3.1)(h)).
Strong evidence: Requires discussion and agreement that the means were seriously considered; does not require that any means be accepted, available in practice, or provided.
Source: Criminal Code s. 241.2 (consolidation current to 2026-09-30) Link to this fact
Laws and loopholes / Other evidence
If neither assessor has expertise in the condition causing the person's suffering, the Track Two safeguards require one of them to consult a practitioner who has that expertise and share the results with the other (s. 241.2(3.1)(e.1)).
Strong evidence: Expertise may come from an assessor or from a consultation; the text does not require an assessor to hold it personally. The statute does not define 'expertise'.
Source: Criminal Code s. 241.2 (consolidation current to 2026-09-30) Link to this fact
Laws and loopholes / Other evidence
Section 241.2(2) defines a grievous and irremediable medical condition as a serious and incurable illness, disease or disability, an advanced state of irreversible decline in capability, and enduring physical or psychological suffering that is intolerable to the person and cannot be relieved under conditions they consider acceptable; all three must be met.
Strong evidence: Statute text as consolidated to 2026-09-30.
Source: Criminal Code s. 241.2 (consolidation current to 2026-09-30) Link to this fact
Laws and loopholes / Other evidence
Section 241.2(1) requires eligibility for government-funded health services, age 18 or older with capacity, a grievous and irremediable medical condition, a voluntary request not made as a result of external pressure, and informed consent after being informed of the means available to relieve suffering, including palliative care.
Strong evidence: Statute text as consolidated to 2026-09-30.
Source: Criminal Code s. 241.2 (consolidation current to 2026-09-30) Link to this fact
Laws and loopholes / Other evidence
Justice Canada says that since March 17, 2021, Canadian MAID law no longer requires a person's natural death to be reasonably foreseeable; the procedural safeguards differ by whether it is.
Strong evidence: Agency's own description of the law; the binding text is Criminal Code s. 241.2. Law changes, so cite the capture date.
Source: Justice Canada: Canada's MAID law (captured 2026-10-21), Justice Canada web page Link to this fact
Laws and loopholes / Other evidence
For people whose natural death is not reasonably foreseeable, the government says the eligibility assessments must take at least 90 days, shortened only if the person is about to lose decision-making capacity and both assessments are complete.
Strong evidence: Agency summary of the statute; the 90-day text is in s. 241.2(3.1).
Source: Justice Canada: Canada's MAID law (captured 2026-10-21), Justice Canada web page Link to this fact
Laws and loopholes / Other evidence
Under the Track Two safeguards, the person must be informed of available and appropriate means to relieve their suffering, including counseling, mental health and disability support services, community services and palliative care, and be offered consultations with those professionals.
Strong evidence: States a duty to inform and offer, not a duty to provide the services or to find housing.
Source: Justice Canada: Canada's MAID law (captured 2026-10-21), Justice Canada web page Link to this fact
Laws and loopholes / Other evidence
Track Two requires two independent assessors and, if neither has expertise in the condition causing the suffering, consultation with a practitioner who does.
Strong evidence: The requirement is expertise in the condition present in the process, not necessarily in one of the two assessors.
Source: Justice Canada: Canada's MAID law (captured 2026-10-21), Justice Canada web page Link to this fact
Laws and loopholes / Other evidence
Justice Canada says MAID is not available where mental illness is a person's sole underlying medical condition until March 17, 2027 ('The eligibility date for persons suffering solely from a mental illness is now March 17, 2027'), after delays by Bill C-39 (2023) and Bill C-62 (February 29, 2024).
Strong evidence.
Caveats
Page captured 2026-10-21 (modified 2026-09-22); the date can change again and a parliamentary review is required. The page's exclusion covers conditions primarily treated in psychiatry, not neurocognitive or neurodevelopmental disorders.
Source: Justice Canada: Canada's MAID law (captured 2026-10-21), Justice Canada web page Link to this fact
Laws and loopholes / Other evidence
The government lists eligibility as a serious and incurable illness, disease or disability, an advanced state of irreversible decline in capability, and enduring and intolerable physical or psychological suffering that cannot be alleviated under conditions the person considers acceptable, plus capacity, voluntariness and informed consent.
Strong evidence: The criteria describe the condition's seriousness and effects; the page names no diagnosis. Whether a given person meets them is decided by assessors, not by this page.
Source: Justice Canada: Canada's MAID law (captured 2026-10-21), Justice Canada web page Link to this fact
Laws and loopholes / Government agency
The US workplace safety regulator, OSHA, says in its own guidance that it has no general indoor-air-quality standard; it offers guidelines on common complaints such as temperature, humidity, lack of outside air and smoking.
Strong evidence: A 2011 publication; verify current OSHA position before quoting as present policy. The booklet is advisory and creates no legal obligations.
Source: OSHA 3430-04, 2011 Link to this fact
Laws and loopholes / Other evidence
The specific OSHA rules OSHA lists as relevant to indoor air are ventilation (29 CFR 1910.94), air contaminant limits (1910.1000), formaldehyde (1910.1048) and laboratory chemicals (1910.1450); none is a fragrance or general IAQ rule.
Strong evidence: List is OSHA's 2011 'some of the applicable' standards, not exhaustive.
Source: OSHA 3430-04, 2011 Link to this fact
Laws and loopholes / Other evidence
Building ventilation standards from ASHRAE (62.1 and 55) are consensus guidance, not OSHA regulations, and ASHRAE 62.1 counts air as acceptable when 80% or more of occupants do not express dissatisfaction.
Strong evidence: The 80% criterion is a population comfort target based on odor studies, not a protection level for sensitive individuals.
Source: OSHA 3430-04, 2011 Link to this fact
Laws and loopholes / Other evidence
OSHA lists perfumes and colognes, cleaning products, pesticides and personal-care products among sources of workplace indoor air pollutants, but sets no limit or rule for any of them.
Strong evidence: Mentions are brief source lists; fragrance is not named as a category, and no health data are given.
Source: OSHA 3430-04, 2011 Link to this fact
Laws and loopholes / Other evidence
EFSA kept the acceptable daily intakes for the six colors tested (sunset yellow, tartrazine, carmoisine, Ponceau 4R, quinoline yellow, allura red) and for sodium benzoate unchanged, saying the trial's lack of consistency, weak effect and unknown clinical meaning made it an insufficient basis for change.
Strong evidence: It is the Panel's weighing of the evidence in 2008, not a finding of no effect; it did not assess later studies.
Laws and loopholes / Other evidence
Since 20 July 2010, EU food containing sunset yellow (E 110), quinoline yellow (E 104), carmoisine (E 122), allura red (E 129), tartrazine (E 102) or Ponceau 4R (E 124) must carry the warning 'may have an adverse effect on activity and attention in children', except meat health marks and egg stamping; a food-color finding, not a fragrance one.
Strong evidence: Original 2008 text; later amendments are not in this capture, so check the current consolidated text. The Regulation states no evidence for the warning.
Source: EU Reg 1333/2008 Link to this fact
Laws and loopholes / Other evidence
EU law lets a food additive onto the approved list only if it poses no safety concern on the available evidence at the proposed level, there is a reasonable technological need that other practicable means cannot meet, and its use does not mislead the consumer.
Strong evidence: Describes the legal test, not how strictly it has been applied in practice.
Source: EU Reg 1333/2008 Link to this fact
Laws and loopholes / Other evidence
EU food flavorings are carved out of the food-additives regulation and governed by a separate regulation (1334/2008); the colors warning in Reg 1333/2008 therefore says nothing about flavorings.
Strong evidence: Additives used inside flavorings are still covered by 1333/2008 (Annex III Part 4, not captured here).
Source: EU Reg 1333/2008 Link to this fact
Skin allergy / Review of other studies
EU scientific advisers (SCCS 2012) list 82 fragrance ingredients as established causes of skin allergy in people.
Strong evidence.
Caveats
Primary now ingested (SCCS/1459/11): 82 = 54 single chemicals + 28 natural extracts on clinical evidence alone, including the 26 labeled in 1999; the count measures reported allergy evidence, not safety.
Source: Kumar 2020 (SCCS 2012), Journal of Cosmetic Dermatology Link to this fact
Skin allergy / Measured in people or real products
In 658 Danish/Swedish patients with hand eczema, 67 (10.2%) reacted to fragrance chemicals commonly found in household products, and the standard fragrance-mix patch test alone would have missed more than half of these reactions.
Strong evidence.
Caveats
Clinic-referred hand-eczema population, not the general public. Confirmed directly against the full primary (Heydorn et al. 2003, Contact Dermatitis 48:317-323), not just its PubMed abstract or Kumar 2020's secondary table.
Source: Kumar 2020 (Heydorn 2003), Journal of Cosmetic Dermatology Link to this fact
Skin allergy / Measured in people or real products
The fragrance chemicals most often found in household products were mostly not in the standard fragrance-allergy patch test used at the time: 6 of its 8 chemicals were in 12% of products or fewer.
Strong evidence.
Caveats
Frequency in products is not the same as clinical sensitization rate; FM II and hydroperoxide testing later added. Clinically confirmed in Heydorn et al. 2003 (n=658 hand-eczema patients, 3 centers): only 3 of the 14 chemicals selected from this paper's household-product survey were FM I constituents, and FM I caught only 45.5% of the fragrance-allergic patients (5.6% of all patients tested missed). The exposure-frequency leader, limonene (78% of products), caused only 0.8-0.9% oxidized-limonene reactivity clinically — product frequency of a chemical still does not predict its clinical allergy rate.
Source: Rastogi 2001, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Common scent chemicals such as linalool hardly cause allergy when fresh, but once exposed to air they form new chemicals that do: in 1,511 dermatitis patients at six European clinics, 1.3% were allergic to air-oxidized linalool (later studies with a stronger test found about 7%).
Strong evidence.
Caveats
Dermatitis patients, not general population; 2005 test concentration (2.0% pet.) was later shown too low. Clinical relevance no longer just inferred: Andersch Björkman 2014 (ROAT) shows patients identified this way go on to develop dermatitis from twice-daily use of a cream/perfume containing oxidized linalool at concentrations as low as 0.3% (0.056% linalool hydroperoxides, ~27 µg/cm²) — inside the 0.1–2% range measured for individual fragrance ingredients in real products.
Skin allergy / Animal study
Common fragrance chemicals such as limonene (citrus) and linalool (lavender) react with air to form far stronger skin allergens; in mouse tests, oxidized limonene was about 10 times more potent than fresh limonene.
Strong evidence: Mouse LLNA potency; review of replicated data.
Skin allergy / Measured in people or real products
In European skin clinics, 2.8-5.2% of patients tested for dermatitis reacted to oxidized limonene.
Strong evidence: Consecutive dermatitis patients, not general population.
Skin allergy / Measured in people or real products
In patch tests of 2,900 dermatitis patients in six countries, 5.2% were allergic to oxidized limonene and 6.9% to oxidized linalool, two of the most common fragrance chemicals.
Strong evidence: Clinic population, not general public.
Source: Bråred Christensson 2016, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Fresh limonene and linalool rarely cause allergy; the allergens form when these chemicals react with air, which also happens in essential oils and perfumes during storage.
Strong evidence.
Caveats
A '0.1-0.3% of patients' figure was removed because it does not trace to a source in our evidence base. Parent-compound sensitization rates are low but vary by dataset; see the Dittmar 2019 entry for oxidized-terpene positive rates.
Source: Bråred Christensson 2016, Contact Dermatitis Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In 2,900 dermatitis patients tested at nine clinics in Europe, Asia, and Australia, 6.9% were allergic to air-oxidized linalool, the form a common floral scent chemical found in most perfumes, cosmetics, and many cleaners takes after contact with air.
Strong evidence: Dermatitis patients, not general population; 72% weak reactions; range 3-14% by clinic.
Source: Christensson 2012, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
60.5% of patients allergic to oxidized linalool would never have learned they had a fragrance allergy from the standard fragrance patch tests.
Strong evidence: Dermatitis patients.
Source: Christensson 2012, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
80% of patients allergic to oxidized linalool whose products were checked were using fragranced products, mainly shampoos, soaps, and creams.
Strong evidence.
Caveats
Linalool confirmed in their products in 38%; clinical relevance established in 41%. Andersch Björkman 2014 (ROAT), drawn from this same 2,900-patient cohort's Gothenburg patients, causally confirms the exposure-effect link: repeated open application of oxidized-linalool-containing cream/perfume at real-product concentrations (down to 0.3%) reproduced dermatitis, and participants who had already avoided linalool-containing products mostly reported improvement.
Source: Christensson 2012, Contact Dermatitis Link to this fact
Skin allergy / Review of other studies
Limonene and linalool become skin allergens when they react with air: in European dermatitis clinics, 3.9-20% of patients tested reacted to oxidized linalool and 1.4-13.7% to oxidized limonene, against under 1% for the fresh chemicals.
Strong evidence: Clinic patients referred for patch testing, not general population.
Skin allergy / Review of other studies
Standard allergy tests with fresh limonene and linalool miss most of these allergies, so European experts now recommend adding the oxidized forms to routine patch testing.
Strong evidence.
Skin allergy / Measured in people or real products
Among 5,773 people tested for eczema at a Swedish hospital, 9.4% were allergic to the air-oxidized forms of two of the most widely used scent chemicals: linalool (7.0%) and limonene (5.1%).
Strong evidence: Clinic population referred for suspected contact allergy; single center.
Skin allergy / Review of other studies
Scent chemicals such as limonene and linalool rarely cause skin allergy when fresh, but once exposed to air they form much stronger allergens; products and oils kept open or stored a long time can contain more of them.
Strong evidence.
Caveats
Review of experimental and clinical work; no new data. Hydroperoxide content depends on storage, light, air exposure and antioxidants; no study here shows that a product's age alone predicts content, so do not claim 'older means worse'.
Source: Karlberg & Lepoittevin 2021, Contact Dermatitis Link to this fact
Skin allergy / Measured in people or real products
Even the fragrance industry's own safety institute classes the cinnamon-scent chemicals cinnamal and cinnamyl alcohol as human skin sensitizers: in its volunteer tests, 29 of 451 people became allergic to cinnamal at 1% or more.
Strong evidence: Industry-run HRIPT/maximization panels, mostly unpublished RIFM reports; 0/≈200 sensitized at ≤0.5%.
Source: RIFM Expert Panel 2005, Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
In people already allergic to cinnamal, a deodorant with just 0.01% of it triggered a reaction in 1 of 9, and 0.032% in 4 of 9; the industry limit is 0.05%, and it was set to prevent new allergies, not reactions in people already sensitized.
Strong evidence.
Caveats
Confirmed by the primary source, now in our evidence base: Bruze et al. 2003, an independent (non-industry, no COI declared), double-blind provocation study with a 20-patient non-allergic control group (0/20 reacted) and P<.001 statistics tying the reaction to both cinnamal-sensitization and the actively-scented axilla. The study's own authors recommend a deodorant limit below 0.01%, stricter than the 0.05% IFRA cap.
Source: RIFM Expert Panel 2005 (citing Bruze 2003), Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
The fragrance industry's own safety review of the rose ketone cis-beta-damascone records that 10 of 50 human volunteers became sensitized when it was patch tested at 5%, and that the test had to be stopped early because of the number of skin reactions.
Strong evidence: 5% is roughly 100x a fine-fragrance use level (max reported 0.02%); at 0.05% two panels gave 0/53 and 0/28.
Source: Lalko 2007 (RIFM), Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
Rose ketones are a real but uncommon allergen: 0.5% of 1606 consecutive European patch-test patients reacted to a 0.2% damascone mixture, and none of 202 Japanese dermatitis patients reacted at 2%.
Strong evidence: Clinic populations, elicitation prevalence not induction risk; original data are Frosch 2002 and Kozuka 1996, reported via the RIFM review.
Source: Lalko 2007 (RIFM), Food and Chemical Toxicology Industry-funded Link to this fact
Skin allergy / Measured in people or real products
About 1 in 5 people in the general population (20.1% of 20,107 people patch tested in 28 studies) are allergic to at least one common chemical that touches the skin, such as nickel, fragrance, preservatives, or hair dye.
Strong evidence: Meta-analysis, very high heterogeneity (I2 97%); mostly nickel; publication bias detected.
Skin allergy / Measured in people or real products
After nickel, the standard fragrance allergy test (Fragrance Mix I) was the most common positive in the general population: about 3.5% reacted, across 19 studies and 19,440 people.
Strong evidence: Pooled 1966-2017 (CI 2.1-5.4%); the largest modern study found 1.8-2.6% for the same test.
Skin allergy / Review of other studies
The standard fragrance patch test covers only 8 of the 82 fragrance chemicals known to cause allergy in people, so any single test undercounts fragrance allergy.
Strong evidence: Authors' discussion; oxidized limonene/linalool never tested in a general-population sample.
Skin allergy / Measured in people or real products
Among about 4,100 North American patients referred for allergy patch testing in 2019–2020, 12.8% reacted to the standard fragrance mix and 11.1% to oxidized linalool, both among the ten most common skin allergens and both up from 2017–2018.
Strong evidence: Referral population, not the general public; primary is DeKoven 2023 (NACDG), cited by the review.
Skin allergy / Review of other studies
Common fragrance ingredients such as limonene and geraniol turn into stronger skin allergens when they react with air in an opened bottle.
Strong evidence: Review relay only; the numbers come from the primary autoxidation studies on the transformation-products hub.
Source: Khalid & Abdollahi 2021, Iranian Journal of Pharmaceutical Research Link to this fact
Skin allergy / Measured in people or real products
The industry's safety panel cleared linalool, a lavender-scented chemical in most fragranced products, as raising 'no safety concerns' after testing the fresh chemical; independent clinics later found that air-exposed (oxidized) linalool causes allergic reactions in about 7% of patients patch-tested for skin allergy (2,900 patients in 9 centers; 5,773 in Sweden, with rates rising).
Strong evidence: Clinic rates are in dermatitis patients, not the general population; test preparations debated; fresh linalool is genuinely a weak sensitizer.
Source: Bickers 2003 (RIFM Expert Panel), Regulatory Toxicology and Pharmacology Industry-funded Link to this fact
Information, not medical advice. See also: myths we won’t tell you.