L'Association pour la santé environnementale du Québec / Environmental Health Association of Québec

Do you suffer from multiple chemical sensitivities?

We want to let you know that you are not alone!

If you have reactions to chemicals, foods, mould, and other things that you used to be able to tolerate and have now lost tolerance for (either over time or suddenly), and you need a diagnosis and assistance, please contact us


Phone: 514 332 4320

What are multiple chemical sensitivities (MCS)?

Multiple Chemical Sensitivity is triggered by exposures to fragrances and to commonly used products, such as personal care, cleaning and laundry products, and “deodorizers” as well as chemicals emitted from building materials and furnishings.

Exposure to these chemicals results in symptoms that include brain fog, breathing difficulties, pain, fatigue, cardiac, urinary, musculoskeletal, and gastrointestinal effects. People with MCS also have a higher incidence of comorbid chronic medical conditions, compared to the general population.

There is no known cure. Therefore, MCS must be properly managed, which primarily consists of avoiding exposures, especially at home and at work, by using least toxic products and promoting healthy spaces.

Like many disabled people in Canada, people with MCS report systemic social and economic inequality. Their disability is often not accommodated, and so they lose their employment, and have difficulty accessing health care and other essential services. They have high rates of food and housing insecurity. They often live below the poverty line, and are isolated and stigmatized. They commonly experience lack of security of person and a lack of quality of life.


Over the past 20 years, Canada’s population has increased by 24%, but the MCS population has increased by more than 100%. 72% are women, and 49% are over the age of 55. This disability encompasses the full spectrum of all disabilities and touches all ages, genders, communities, and vulnerable populations.

Multiple Chemical Sensitivity (MCS), population 12 years and more, Québec

Multiple Chemical Sensitivity (MCS)Number, 2020%, 2020Number, 2016%, 2016Number, 2015%, 2015
Québec251,0003.4230 5003.2173 5002.5

Source: Canadian Community Health Survey, Statistics Canada

Examples of triggers / exposures (Non exhaustive list)

Click here to view more triggers

Chemical agentsFlame retardants, rubber, volatile organic compounds (VOCs), diesel, ink and printed material, petrol or natural gas, smoke (tobacco, wood, etc.), vehicle exhaust, fresh tar or asphalt, interiors of new cars, dry cleaning fluid, building and renovation materials (e.g. caulking, grout, shellac, paint, sealants, varnish, etc.), markers, new furniture and furnishings, new carpets, pesticides , petrochemicals, insecticide spray, shower curtains, chemicals and VOCs released by new products, nail polish and solvents, soft vinyl, etc.
Biological agentsMould
Glues and solvents, exposures to volatile organic compounds (VOCs), exposures to gases and fumes (firefighters), gases and fumes from welding, exhaust gases, Isocyanates, paints and paint thinners, pesticides, dust from wood, flour, metal, etc., chemicals used in the manufacture of plastics, adhesives, etc.
Scented productAir fresheners and incense, fabric softeners, sunscreen, detergents and soaps, new plastic, cleaning products (e.g. disinfectants, bleach, floor cleaners, furniture cleaners, etc.), personal care products (e.g. : deodorants, hair spray, body lotions, aftershave lotions, makeup, etc.), baby care products, perfumed products (colognes, essential oils, perfumes, devices emitting all kinds of perfumes, potpourris), etc.
OtherFoods, supplements, medications, food flavourings, colours, preservatives, etc., sound, vibration, light, temperature, wood terpenes, etc.

This is not an exhaustive list of exposures. Sensitivities caused by a substance can lead to reactions to other chemicals, including unrelated personal and household cleaning products, smoke, food, etc.

Symptoms (Non-exhaustive list)

Click here to view symptoms

Central Nervous &
Sense of smell heightened, neurological pain (skin burning most often), migraines, intense headaches, dizziness, vertigo, confusion, feeling dull, weak or foggy, lack of coordination and/or balance, tinnitus, cognitive problems (brain fog), poor concentration, difficulty remembering, memory loss, hyperactivity, restlessness, anxiety, tension, depression, insomnia, sleep problems, night sweats, fatigue, exhaustion
Respiratory & ImmuneDistress and/or difficulty breathing, coughing, wheezing, shortness of breath, asthma, chest pain, frequent bronchitis or pneumonia, congestion, itching or runny nose, allergic rhinitis, sinus infections and/or pain, sore throat, swollen glands, flu-like symptoms
EyesRed, painful, dark circles, watery eyes, disturbed vision
GastrointestinalExcessive drooling, bleeding gums, heartburn, abdominal or stomach pain, nausea, bloating, constipation, diarrhea
EndocrineFatigue, lethargy, fluctuating blood sugar, hormonal disturbances or imbalances
Musculo skeletalMuscle spasms and / or pain, joint pain and / or swelling, backache, burning sensation in the muscles, extreme pain in the face, jaws and mouth, weakness, allodynia, inflammation
CardiovascularPalpitations, rapid and / or irregular heartbeat, hypertension or hypotension, cold extremities
SkinEczema, rashes, itching, hives, redness, rash, redness, cuts or lesions
GenitourinaryFrequency and urgency to urinate, incontinence, spasms in the bladder

Diagnostic criteria

Taking an Exposure History (CH2OPD2)

The Quick Environmental Exposure and Sensitivity Inventory (QEESI)

Multiple Chemical Sensitivities (MCS)

Initiation and subsequent sensitization observed in cases of environmental sensitivities:

  1. Symptoms are reproducible following repeated chemical exposure;
  2. The condition is chronic;
  3. Lower exposure levels than those previously tolerated, or tolerated by the general population, lead to the manifestation of symptoms;
  4. Symptoms improve or disappear when the incitants are removed;
  5. Responses occur to multiple chemically unrelated substances;
  6. Symptoms involve multiple organ systems;
    • Still not refuted in the literature published almost two decades later
    • Definition used both in clinical practice and in research
    • Recently (2018) confirmed by the MOHLTC of Ontario by a group of experts using the Delphi process

Bartha, L., et al., Multiple chemical sensitivity: a 1999 consensus. Archives of Environmental Health: An International Journal, 1999. 54(3): p. 147-149.
McKeown-Eyssen, G.E., et al., Multiple chemical sensitivity: discriminant validity of case definitions. Archives of Environmental Health: An International Journal, 2001. 56(5): p. 406-412.
Nethercott, J.R., et al., Multiple chemical sensitivities syndrome: toward a working case definition. Archives of Environmental Health: An International Journal, 1993. 48(1): p. 19-26.
Ontario Ministry of Health and Long-Term Care, Guiding Principles for the Diagnosis of Environmental Sensitivities/Multiple Chemical Sensitivity. Centre for Effective Practice, 2018