Your allergy tests can come back normal, and a scented room can still make breathing hard. The studies below show that allergy status didn’t explain who reacted, and that a few small studies found unusual cough sensitivity in people with normal tests. Some chamber studies also found that sulfur dioxide and sulfuric acid, two irritant gases that aren’t fragrance chemicals, caused severe airway narrowing in people with asthma at or below workplace exposure limits.
Evidence key Strong Moderate Weak How we grade
Allergy didn’t explain who reacted
Start with the study that asked who reacted to fragrance and what predicted it.
Standard allergy tests did not predict who reacted to fragrance; people with sensitive airways (including non-allergic asthma) were 2-4 times more likely to react, pointing to airway irritation rather than classic allergy. Moderate evidence. Elberling 2005
A household-spray cohort showed the same pattern. It is not about fragrance alone.
The household-spray-asthma association was not modified by atopy (allergic sensitization): risk was similar in atopic (RR 1.30) and non-atopic (RR 1.33) participants, supporting an irritant rather than allergic mechanism. Moderate evidence. Zock et al. 2007
The same pattern shows up with a lab gas.
Atopic (allergic, IgE-sensitized) volunteers without asthma were essentially as unresponsive to sulfur dioxide exposure as non-atopic normal volunteers; airway hyperreactivity (asthma), not IgE-mediated allergy/atopy, was what predicted reaction to this irritant gas. Moderate evidence. Linn et al. 1987
Retest the same people weeks later and the result held up. The usual labels did not predict it well.
An individual's sensitivity to a given dose of an irritant gas (sulfur dioxide) was highly reproducible when the same person was retested 1-7 weeks later (r=0.85 across all subjects, r=0.82-0.74 within asthmatic subgroups), even though that sensitivity could not be predicted well from a clinical asthma diagnosis, allergy skin testing, or serum IgE level. Moderate evidence. Linn et al. 1987
A review of controlled chamber studies found the same.
A review of controlled chamber studies (carbon dioxide, ammonia, formaldehyde, sulfur dioxide, glycol/glycol-ether mixtures) found no consistent evidence that people with allergic rhinitis or mild asthma are more sensitive to sensory-irritant chemicals than non-allergic people. Moderate evidence. Nielsen & Wolkoff 2017 Industry-funded
Small studies of cough sensitivity
Both of these are small studies.
In a small Swedish clinic study, people whose breathing symptoms were triggered by scents and chemical irritants — but who had normal lung function and negative allergy and asthma tests — coughed much more after inhaling capsaicin (the hot-pepper compound) than either people with verified asthma or healthy volunteers (93 vs 23 average coughs at the highest dose, P<0.001). Moderate evidence. Millqvist, Bende & Löwhagen 1998
In a small double-blind, randomized lab test (Ternesten-Hasséus 2002, the primary study behind this review's capsaicin-challenge claim), 12 people with multiple chemical sensitivity coughed significantly more than 12 matched healthy controls at every capsaicin dose tested (P<0.05 to P<0.005), a sign that their airway irritant nerves are oversensitive. Moderate evidence. Molot 2023
Lab and animal work proposes one possible mechanism.
Many everyday chemicals, including some released by scented and cleaning products, act on the same irritant-sensor nerves in the nose and airways (TRPA1 and TRPV1), one reason very different products can cause similar symptoms. Weak evidence. Molot 2023
In lab studies, inflammation lowers the threshold for this irritant receptor, a proposed reason scent reactions can be worse when airways are already inflamed. Weak evidence. Mihara & Shibamoto 2015
At work: cleaners and other irritants, not perfume specifically
These studies concern cleaning products, quaternary ammonium compounds, and general workplace irritants.
Cleaning products were the suspected exposure in 236 of 1,915 (12%) confirmed work-related asthma cases across California, Massachusetts, Michigan, and New Jersey, 1993-1997; most were new-onset asthma (80%) and about a fifth were consistent with reactive airways dysfunction syndrome, an irritant-induced, non-allergic asthma type. Moderate evidence. Rosenman 2003
Only 6.5% of tested healthcare workers (32 of 494) had detectable specific IgE antibodies to quaternary ammonium compounds, and this was not significantly associated with reported asthma, new-onset asthma, or nasal symptoms — despite QAC exposure itself being strongly associated with those same outcomes. The study authors read this pattern as pointing to an irritant, not an IgE-mediated allergic, mechanism. Moderate evidence. Gonzalez 2014
A systematic review of workplace irritants found that people with pre-existing airway sensitivity (atopy plus non-specific bronchial hyper-responsiveness) can develop new-onset asthma from chronic, repeated exposure to an irritant at concentrations below the official occupational exposure limit. Moderate evidence. Baur, Bakehe & Vellguth 2012
The workers were challenged with commercial cleaning products that contained mixtures of irritants and possible sensitizers, so the authors could not formally identify which ingredient caused each reaction. Moderate evidence. Vandenplas 2013
Below the limit isn’t the same as safe
Neither finding is about fragrance chemicals. Both concern sulfur dioxide and sulfuric acid, and the second gives the numbers behind the first. “Below the limit” sounds like a promise. For someone with asthma, the chamber studies say otherwise.
Being below a standard occupational exposure limit does not mean an irritant gas is safe for someone with asthma: chamber studies found severe asthma attacks from sulfur dioxide and sulfuric acid at concentrations at or below typical workplace limits for those substances. Moderate evidence. Johansson 2016
Chamber studies show irritant gases cause severe airway narrowing in people with asthma at concentrations at or below standard workplace exposure limits: asthmatics had severe bronchoconstriction to sulfur dioxide at about 0.4 ppm (1.1 mg/m3) after just 5-10 minutes of exercise, and to sulfuric acid at about 1 mg/m3. Strong evidence. Kleinbeck & Wolkoff 2024 Industry-funded
What we can’t tell you yet
We haven’t found a graded study that says what share of scent-triggered breathing problems is irritant rather than allergic. The evidence on people with chemical intolerance has its own limits.
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
The cough-sensitivity studies are small and come from one research program. The rest has other limits: self-reported exposure, single cohorts, and findings about irritants that aren’t fragrance. We’ll update this page if a better source turns up.
A research test, not routine care
People whose breathing symptoms are triggered by scents or chemical irritants, but whose standard asthma tests (spirometry, methacholine challenge) come back normal, can ask a specialist about objective sensory-hyperreactivity testing, such as a capsaicin cough-sensitivity challenge, rather than assuming the symptoms are either undiagnosed asthma or purely psychological. Weak evidence. Millqvist, Bende & Löwhagen 1998
What you can do
- A reaction doesn’t need an allergy to be real, and it doesn’t need a diagnosis to deserve a scent-free space. Ask for one.
- Start with Allergy or irritation? and see fragrance and your airways and fragrance and asthma.
- If the problem is at work, read your rights at work.
- Want the wider argument? See Allergy or irritation? Why the studies keep pointing to irritation
Every claim above shows its evidence grade and names its source. This is information, not medical advice.