Prevalence of MCS

flower33For compilation by MCSer Linda Sepp of Canada, go to

For a comprehensive study done by the Government of Australia in 2010, go

Lacking and direly needed:  toxicogenome epidemiologic research.  However, it is difficult to conduct such research due to the (1) extremely low levels of sensitivities may be involved, (2) the multiplicity of chemical agents to which sensitivities are claimed, and (3) the lack of objective laboratory markers to quantify these sensitivities.

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US Prevalence Studies for MCS

J Environ Health. 2009 Mar;71(7):46-50.

Prevalence of fragrance sensitivity in the American population.  (2009)


This study determined the percentages of individuals who report adverse effects from exposure to fragranced products in the U.S. population and in subpopulations of those with asthma or chemical sensitivity. Data were collected through telephone interviews from two geographically weighted, random samples of the continental U.S. in two surveys during 2002-2003 and 2005-2006 (1,057 and 1,058 cases, respectively). Respondents were asked if they find being next to someone wearing a scented product irritating or appealing; if they have headaches, breathing difficulties, or other problems when exposed to air fresheners or deodorizers; and if they are irritated by the scent from laundry products, fabric softeners, or dryer sheets that are vented outside. Results aggregated from both surveys found that 30.5% of the general population reported scented products on others irritating, 19% reported adverse health effects from air fresheners, and 10.9% reported irritation by scented laundry products vented outside. This study reveals that a considerable percentage of the U.S. population reports adverse health effects or irritation from fragranced products, with higher percentages among those with asthma and chemical sensitivity.

Comment in

Arch Environ Health. 2004 Jun;59(6):300-5.

Asthma and chemical hypersensitivity: prevalence, etiology, and age of onset.  (2006)


This study investigates asthma’s national prevalence and potential overlap with chemical hypersensitivity. It also examines asthma’s etiology, age of onset, and demographic characteristics. Data were collected from a geographically weighted random sample of the continental U.S. (1058 cases), in four seasonal cohorts (2005-2006). The study found that 12.9% of the sample report asthma, 11.6% report chemical hypersensitivity, and 31.4% of those with asthma report chemical hypersensitivity. Among asthmatics, 38% report irritation from scented products, 37.2% report health problems from air fresheners, and 13.6% report their asthma was caused by toxic exposure. Asthma cases affected each racial/ethic group in roughly the same proportion, with nearly 50% classified as childhood onset.

PMID:  19318506




The authors conducted a telephone survey of 1054 randomly selected individuals within the continental United States to determine the prevalence of chemical hypersensitivity and the medical diagnosis of multiple chemical sensitivity (MCS) in the American population. The etiology and symptomatology of MCS also were investigated. Results produced a 95% confidence level and a +/-3% margin of error. The authors found that 11.2% of Americans reported an unusual hypersensitivity to common chemical products such as perfume, fresh paint, pesticides, and other petrochemical-based substances, and 2.5% reported they had been medically diagnosed with MCS. Additionally, 31.1% of those sampled reported adverse reactions to fragranced products, and 17.6% experienced breathing difficulties and other health problems when exposed to air fresheners. Although chemical hypersensitivity was more common in women, it affected individuals in all demographic groups studied.

PMID: 16238164


Arch Intern Med. 2000 Apr 24;160(8):1169-76.

Multiple chemical sensitivity syndrome: symptom prevalence and risk factors in a military population.  (2000)



To assess the prevalence of and risk factors for self-reported symptoms suggestive of multiple chemical sensitivities/idiopathic environmental intolerance (MCS/IEI) in Persian Gulf War (PGW) veterans from Iowa and a comparison group of PGW-era military personnel.


A population-based sample of Iowa military personnel was surveyed using a cross-sectional telephone interview. Study participants were randomly drawn from 1 of 4 domains: PGW active duty, PGW National Guard/Reserve, non-PGW active duty, and non-PGW National Guard/Reserve. A complex sample survey design was used selecting participants from the following substrata: age, sex, race, rank, and military branch. The criteria for MCS/IEI were developed using expert consensus and the medical literature.


A total of 3695 study participants (76% of those eligible) completed the telephone survey. The prevalence of symptoms suggestive of MCS/IEI in all participants was 3.4%. Veterans of the PGW reported a significantly higher prevalence of symptoms suggestive of MCS/IEI than did non-PGW military personnel (5.4% vs 2.6%); greater sensitivity to organic chemicals, vehicle exhaust, cosmetics, and smog; and more lifestyle changes. The following risk factors for MCS/IEI were identified with univariate analysis: deployment to the Persian Gulf, age (>25 years), female sex, receiving a physician diagnosis of MCS, previous professional psychiatric treatment, previous psychotropic medication use, current psychiatric illness, and a low level of preparedness. Multiple logistic regression analysis identified several independent risk factors for MCS/IEI, including deployment to the Persian Gulf, age, sex, rank, branch of service, previous professional psychiatric treatment, and current mental illness.


Self-reported symptoms suggestive of MCS/IEI are relatively frequent in a military population and are more common among PGW veterans than comparable controls. Reported chemical sensitivities and accompanying behavioral changes were also frequent. After adjusting for age, sex, and training preparedness, previous professional psychiatric treatment and previous psychotropic medication use (before deployment) showed a robust association with symptoms suggestive of MCS.

PMID:  10789611

Prevalence of people reporting sensitivities to chemicals in a population-based survey. (1999)


To describe the prevalence and correlates of reports about sensitivities to chemicals, questions about chemical sensitivities were added to the 1995 California Behavior Risk Factor Survey (BRFS). The survey was administered by telephone to 4,046 subjects. Of all respondents, 253 (6.3%) reported doctor-diagnosed “environmental illness” or “multiple chemical sensitivity” (MCS) and 643 (15.9%) reported being “allergic or unusually sensitive to everyday chemicals.” Sensitivity to more than one type of chemical was described by 11.9% of the total sample population. Logistic regression models were constructed. Hispanic ethnicity was associated with physician-diagnosed MCS (adjusted odds ratio (OR) = 1.82, 95% confidence interval (CI) 1.21-2.73). Female gender was associated with individual self-reports of sensitivity (adjusted OR = 1.63, 95% CI 1.23-2.17). Marital status, employment, education, geographic location, and income were not predictive of reported chemical sensitivities or reported doctor diagnosis. Surprising numbers of people believed they were sensitive to chemicals and made sick by common chemical exposures. The homogeneity of responses across race-ethnicity, geography, education, and marital status is compatible with a physiologic response or with widespread societal apprehensions in regard to chemical exposure.

Arch Environ Health. 1996 Jul-Aug;51(4):275-82.



The objectives of this study were (a) to determine the self-reported prevalence of allergy and chemical sensitivity in a rural population of eastern North Carolina, (b) to determine the type and frequency of symptoms for each condition, and (c) to determine the demographic groups affected. A random general telephone survey was conducted during the period May 14, 1993, to September 10, 1993, and questions about allergy and chemical sensitivity were asked. Of the 1 446 households contacted, 1 027 (71%) individuals agreed to participate. Allergies were reported by 365 (35%) individuals. Thirty percent of allergic individuals reported that symptoms occurred once or more each week, whereas 61% reported that symptoms occurred, at most, once each month. Allergic symptoms that occurred daily were reported by 5.3% of the total population. Chemical sensitivity was reported by 336 (33%) individuals. Thirty-five per cent of chemically sensitive individuals reported symptoms at least once each week, whereas 53% reported that symptoms occurred once (or less) each month. Symptoms of chemical sensitivity that occurred daily were reported by 3.9% of the total population. Both allergy and chemical sensitivity were distributed widely across age, income, race, and educational groups. Simultaneous allergy and chemical sensitivity were reported by 16.9% of the population, allergy without chemical sensitivity by 16.0%, chemical sensitivity without allergy by 18.2%, and neither condition by 48.9%. If the prevalence of sensitivity to chemical irritants is, in fact, equivalent to that of allergy, as was found in this study, then support for the scientific investigation of chemical sensitivity is justified.


Rev Mal Respir. 2013 Feb;30(2):99-104. doi: 10.1016/j.rmr.2012.06.016. Epub 2012 Nov 13.

Multiple chemical sensitivity: a diagnosis not to be missed.  (2012)

[Article in French]


Multiple chemical sensitivity (MCS) is a chronic condition, which belongs to the group of medically unexplained syndromes. Patients (men as well as women) complain of many subjective symptoms such as nose and mouth irritation, sore throat, dyspnea, tiredness, dizziness, headache and concentration difficulties. Patient typically report at least four or five symptoms occurring when they are exposed to particular substances, at a very low concentration that usually does not cause symptoms or harm in normal individuals. The common feature of products that appear to be responsible (either occupational or domestic) is that they have a strong smell and include: solvent, paint, glue, tar, oil, pesticides, perfume, cosmetics and spray products. MCS is nowadays considered to be one aspect of idiopathic environmental intolerance (IEI) whose other main aspect is hypersensitivity to electromagnetic fields. If the diagnosis is suspected clinically it can be confirmed using the Quick Environmental Exposure and Sensitivity Inventory (QEESI(©)) self-questionnaire. MCS is often misdiagnosed as asthma or an allergic conditions which means that patients are frequently referred to respiratory and allergy specialists. Misdiagnosis can lead to many futile medical investigations. Psychotherapy can improve quality of life in some cases. Preventive measures are often ineffective and do not stop the condition worsening: hypersensitivity can spread to common environmental odors so that a few people become severely disabled and limited in their workplace as well as in private life. In France, 435 cases were registered in the university hospital occupational disease departments network (RNV3P) during the period 2007-2010. It is therefore important that every clinician be able to recognize the condition and ensure that their patients could get compensation when unable to go on working.

PMID:  23419440  |  Environ Health Perspect. 2003 September; 111(12): 1490–1497  |  PMCID: PMC1241652

A review of a two-phase population study of multiple chemical sensitivities.  Why MCS is physiologic and not psychologic etiology.


In this review we summarize the findings of a two-phase study of the prevalence, symptomatology, and etiology of multiple chemical sensitivities (MCS). We also explore possible triggers, the potential linkage between MCS and other disorders, and the lifestyle alterations produced by MCS. The first phase of the study consisted of a random sampling of 1,582 individuals from the Atlanta, Georgia, metropolitan area to determine the reported prevalence of a hypersensitivity to common chemicals. In this phase, 12.6% of the sample reported a hypersensitivity. Further questioning of individuals with a hypersensitivity indicated that 13.5% (1.8% of the entire sample) reported losing their jobs because of their hypersensitivity. The second phase was a follow-up questioning of the respondents who initially reported hypersensitivity. In this phase, we found that individuals with hypersensitivity experience a variety of symptoms and triggers. A significant percentage (27.5%) reported that their hypersensitivity was initiated by an exposure to pesticides, whereas an equal percentage (27.5%) attributed it to solvents. Only 1.4% had a history of prior emotional problems, but 37.7% developed these problems after the physical symptoms emerged. This suggests that MCS has a physiologic and not a psychologic etiology.


Selected References

These references are in PubMed. This may not be the complete list of references from this article.
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Articles from Environmental Health Perspectives are provided here courtesy of National Institute of Environmental Health Science

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From a Yellow Canary of the 21st century, living in our disabling biosphere