You’re in an elevator or a waiting room, and someone’s scent fills the air. Your head starts to pound, and everyone else seems fine. Some people report getting sick around perfume, scented cleaners, and air fresheners that others shrug off. Researchers study it as chemical intolerance, or multiple chemical sensitivity (MCS). Here’s what surveys and lab studies have found, where the science is still split, and why none of that makes scented products harmless background.
Evidence key Strong Moderate Weak How we grade
Fragrance is a commonly reported trigger
In a small (n=69) follow-up of Atlanta-area adults with chemical hypersensitivity, the products most commonly reported to trigger symptoms were cleaning agents (88.4%), pesticides (81.2%) and perfume (81.2%), followed by tobacco smoke (82.6%) and car exhaust (72.5%). Moderate evidence. Caress & Steinemann 2003 (EHP)
In a 2016 US national survey, 86% of people who said a doctor had diagnosed them with multiple chemical sensitivity reported health problems from fragranced products, most often breathing problems (50%), migraines (47%) and eye/nose symptoms (47%). Moderate evidence. Steinemann 2018 (JOEM)
Among Australians who said they had been diagnosed with multiple chemical sensitivities, 91.5% reported health problems from fragranced products such as air fresheners, scented cleaners, and other people's perfume. Moderate evidence. Steinemann 2018
In one California survey, it also went with asthma.
People with asthma were about 4 times more likely to report a doctor's diagnosis of environmental illness/multiple chemical sensitivity than people without asthma (19.0% vs. 4.6%), and over twice as likely to self-report unusual sensitivity to everyday chemicals (31.5% vs. 13.9%). Moderate evidence. Kreutzer, Neutra & Lashuay 1999
How many people say they’re affected
In a 2002-03 US national telephone survey of 1,054 randomly selected adults, 11.2% self-identified as unusually sensitive to everyday chemicals such as cleaning products, perfume, and detergents, and 2.5% said they had been medically diagnosed with multiple chemical sensitivity (MCS). Moderate evidence. Caress & Steinemann 2003
In a 1995 population-based telephone survey of 4,046 California adults, 15.9% said they were 'allergic or unusually sensitive to everyday chemicals' (like cleaning supplies, paints, perfumes, or soaps) and 6.3% reported a doctor's diagnosis of environmental illness or multiple chemical sensitivity. Moderate evidence. Kreutzer, Neutra & Lashuay 1999
In a national survey of 1,098 Australian adults, 6.5% said a doctor or health professional had told them they have multiple chemical sensitivities, and 18.9% said they are unusually sensitive to everyday chemicals. Moderate evidence. Steinemann 2018
Estimates vary a lot depending on how the question is asked.
Estimated prevalence of multiple chemical sensitivity across the reviewed epidemiological literature ranges from about 1% to more than 15% of the population, a spread the review attributes to diagnostic difficulty, lack of standardized case-definition criteria, and differing recognition of the condition across countries. Weak evidence. Rossi 2018
Reports of doctor-diagnosed multiple chemical sensitivity and self-reported chemical sensitivity were spread fairly evenly across race/ethnicity, income, education, marital status, and geography in a representative California sample, unlike clinic-based case series which have reported a predominance of middle- to upper-class white women. Moderate evidence. Kreutzer, Neutra & Lashuay 1999
What people say it has kept them out of
Now the cost in daily life, as the people surveyed report it.
Among Australians with diagnosed multiple chemical sensitivities, about three in four (77.5%) said a fragranced product had kept them from going somewhere, and about two in three (64.8%) can't or won't use public toilets with air fresheners. Moderate evidence. Steinemann 2018
More than half of Canadians with MCS surveyed (52%) said their current housing exposed them to mold or other symptom-triggering conditions, and 15% (18/119) fell into the paper's homeless category: moving frequently, living in a vehicle or tent, or staying with friends or family. Moderate evidence. Diallo 2026
Many people with chemical sensitivities delay or avoid medical care because clinics and hospitals are heavily scented; healthcare was named as one of the least accessible settings (31 of 60). Moderate evidence. Roy 2026
More in fragrance in hospitals and clinics.
What patients describe
Among 129 clinically diagnosed MCS patients in Rome, hyperosmia and asthenia were the most common symptoms (about 97% and 83% of patients) and clustered together statistically, followed by respiratory symptoms (dyspnea, cough, tachypnea; about 72%) and neurocognitive symptoms (confusion, attention/memory/decision-making deficits; about 62%). Moderate evidence. Del Casale 2020
What the lab studies found
One small Swedish study measured cough.
In a small double-blind lab test, 12 people with multiple chemical sensitivity coughed significantly more than 12 healthy matched controls every time they inhaled capsaicin (the compound that makes chili peppers hot), and the difference grew larger at higher doses. Moderate evidence. Ternesten-Hasséus 2002
The extra coughing in multiple chemical sensitivity patients was not explained by asthma or classic allergy: patients tested negative on standard allergy skin-prick and methacholine airway-reactivity tests, and lung function (FEV1) did not change after capsaicin, pointing to an oversensitive airway nerve response rather than an allergic or asthmatic reaction. Moderate evidence. Ternesten-Hasséus 2002
In a small double-blind lab test, a drug that numbs sensory nerves (lidocaine) cut in half the number of coughs that chemically sensitive patients had after inhaling capsaicin, evidence that their airway sensitivity runs through nerve pathways rather than the kind of airway narrowing seen in asthma. Moderate evidence. Millqvist 2000
In a double-blind lab test where people could not smell it, perfume vapor piped to one eye caused more eye irritation than clean air in 10 of 42 people, including 2 healthy volunteers: perfume can irritate the eyes without being smelled. Moderate evidence. Elberling 2006
One brain-imaging study found differences, though not the ones you might expect.
Odor detection thresholds (n-butanol test) did not differ between MCS subjects and controls (P=0.8), and nasal anatomy was normal in both groups, so normal ability to smell coexisted with abnormal brain and autonomic responses to odors. Moderate evidence. Hillert et al. 2007
In a PET brain-imaging study of 12 women with multiple chemical sensitivity (MCS) and 12 matched controls, MCS subjects activated the brain's core odor-processing regions (amygdala, piriform, and insular cortex) LESS than controls when smelling most odorants, not more, despite resting brain activity being normal in both groups. Moderate evidence. Hillert et al. 2007
MCS subjects showed real, measurable physical changes during odor exposure that controls did not: their heart rate rose (RR interval fell, P<0.0001) and their breathing pattern changed differently from controls specifically while smelling odorants (not odorless air), a difference that held up even after statistically controlling for breathing pattern itself. Moderate evidence. Hillert et al. 2007
Chamber studies looked at irritant chemicals more broadly.
People with chemical intolerance or multiple chemical sensitivity react more strongly than healthy controls in controlled chamber exposures to irritant chemicals, with derived sensitivity factors typically 1 to 3 times higher and, in some studies, up to about 20 times higher. Moderate evidence. Mangelsdorf et al. 2021, Int J Hyg Environ Health
What the blinded studies didn’t show
Other blinded studies found important limits.
Across 6 independent lab studies using a forced-choice 'which one is the real chemical?' test, people who report multiple chemical sensitivities were not better than other people at telling active chemical exposures apart from blank or sham ones. Moderate evidence. Das-Munshi 2006
One chamber study tested healthy women and left out people with clinically significant MCS.
In a double-blind chamber study of 130 healthy women, those who scored high on a validated chemical-odor-intolerance questionnaire did not have worse symptoms, stress-hormone (cortisol) levels, or cognitive/driving-simulation performance when exposed to an indoor VOC or VOC-plus-ozone mixture, compared to women who scored low on the same questionnaire. Moderate evidence. Fiedler 2008
Nobody has settled the cause
A systematic review of 27 human chemical-exposure challenge studies on multiple chemical sensitivity (1998-2015) found no scientific consensus on whether the reaction is physical (toxicological) or psychological: only a minority of studies concluded toxicological causation, a similar minority concluded psychological causation, and the single largest group of studies reached no conclusion at all. Moderate evidence. Rossi 2018
Funding history doesn’t prove bias, but it’s worth knowing.
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. Binkley 2023 Industry-funded
Whatever the cause turns out to be, people report being kept out of places and putting off medical care. Getting into a shop or a clinic shouldn’t depend on tolerating someone else’s scent.
What may help, and what the law says
Asking is hard, and nobody should have to.
Because people with MCS describe both a fear of asking for accommodations (risking hostility) and a fear of staying silent (risking worsening symptoms), workplaces and services that proactively offer fragrance-free accommodation without requiring the person to ask remove one source of this dilemma. Weak evidence. Driesen 2020
In two hand-picked, uncontrolled case studies, cutting fragrance and other chemical sources at home went with lower self-reported symptom scores.
In two of three reported chemical-intolerance case studies, QEESI Chemical Intolerance and Symptoms scores fell substantially after a home intervention that reduced fragrance and other VOC sources (Case 1: 80→43 and 63→23; Case 3: 74→54 and 59→23, each on a 0-100 scale). Weak evidence. Rincón et al. 2024
In the US, disability status is decided person by person.
In 1992, the U.S. Department of Justice held that whether multiple chemical sensitivity (MCS) or "environmental illness" counts as a disability under Section 504 of the Rehabilitation Act (and, by the same analysis, the ADA) is decided case by case, not by diagnosis alone: the test is whether the person's impairment substantially limits a major life activity, given their particular circumstances. Strong evidence. DOJ 1992
For people in HUD-assisted housing, the agency’s own guidance names specific accommodations.
A resident of HUD-assisted housing with a documented chemical sensitivity can cite this HUD exhibit directly when requesting advance notice before common-area cleaning and nonchemical cleaning products where practical, since HUD's own guidance names these as accommodations that are not an undue burden. Moderate evidence. HUD Occupancy Handbook 4350.3 REV-1, Exhibit 2-6 (2007)
What you can do
- Go fragrance-free in shared spaces by default, so nobody has to explain their health to get through the day. Take the pledge to ask for it once this year.
- At work, start with our workplace guide and the evidence on fragrance at work.
- Need to ask an employer, landlord, school, or clinic? The letter builder writes the request for you, and your rights covers the laws.
- Put up a fragrance-free sign, or share what it’s like for you on the story wall.
Every claim above shows its evidence grade and names its source. See all the chemical sensitivity facts and the claims we won’t make. Information, not medical or legal advice.
