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

Multiple Chemical Sensitivity (MCS)

Article by Rohini Peris and Michel Gaudet:

Over one million Canadians have been diagnosed with Multiple Chemical Sensitivities (MCS). Up to 72% are women and close to 50% are seniors (Statistics Canada, 2020).[1] The number of diagnosed cases has been increasing (Statistics Canada, 2000-2020).

MCS is a recognized disability under the Canadian Human Rights Act.[2] Yet it is likely that many people have never heard about this medical condition. Here are some useful facts about the MCS health condition.

What is MCS

Multiple Chemical Sensitivity (MCS) is a chronic condition, which is initiated or started following exposure to substances commonly used in our living spaces. These exposures can be from chemicals contained in products that are used in daily life, such as fragrances, personal care and cleaning products, renovation and construction materials, pesticides, solvents, and even biological contaminants such as mould.[3], [4]

Exposures that can initiate/start MCS can be long term or chronic low-level exposures at home or at the workplace, or even one or more large exposures.[5] This results in sensitization of the individual and exposure to the substance can result in symptoms. Removal of these exposures from the environment of the individual, will result in the person being symptom-free. However, if this is not done, constant exposures can provoke an increased number of symptoms in many body systems, and can also cause the individual to have stronger reactions/symptoms to lower doses of exposure, and to an increased number of unrelated chemicals.

Life for the individual can become very difficult. Imagine getting ill from the chemicals commonly used around us. There literally is no place to run, no place to hide!

If the individual is aware of the occurrence of sensitization and the resulting symptoms, efforts are made to avoid exposures and thus, the ensuing symptoms. At this point it is crucial to have these chemicals (barriers) removed from the person’s living and work spaces. Lack of accommodation and support will result in increased disability. For individuals who do not understand or know what happened to them, finding out the reason for an increasing number of symptoms can be a trying experience.

Medical schools are not training future doctors about this increasing health condition. Unless there is knowledge about the MCS health condition, the person will often remain undiagnosed and will often have to go through a battery of health tests, which often show that the person is in good health. This places the individual at even greater risk as they are often sent to psychiatry and labelled as being mentally ill – when in fact, simply cleaning out their environments would help greatly. This stigmatization makes life increasingly harder for the sufferer and often results in the loss of healthy workplace and home accommodations for their disability of MCS.

At present there is no consensus on a medication treatment plan, and no cure for this medical condition. Avoidance of these triggering substances is the basis for maintenance of health. This includes living in a least toxic environment and also using least toxic products, organic food, clean water and breathing clean air.

The same chemicals that are implicated in global warming, are also making humans ill.

People experiencing MCS often experience loss of employment, poverty, lack of access to essential services including health care, homelessness, isolation and stigmatization.

It is our mission to remove the barriers causing this disability.

Prevention of MCS[6]

To learn how to choose healthy products, visit our website:

To learn more about Multiple Chemical Sensitivities:

Become a member:


Make a donation:

Rohini Peris and Michel Gaudet

[1] Statistics Canada (2020) Canadian Community Health Survey (CCHS).
[2] Canadian Human Rights Commission. (2019). Environmental sensitivity and scent-free policies. Retrieved from