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Multiple Chemical Sensitivity &

Environmental Hypersensitivity

Multiple Chemical Sensitivity (MCS) and Environmental Hypersensitivity (EH) describe a chronic condition whereby a person has symptoms when exposed to certain chemicals or other environmental agents at low levels tolerated by most people. The symptoms may range in severity from mild to debilitating.


MCS has also been called chemical intolerance (CI), environmental hypersensitivity EH), environmental illness (EI), toxicant-induced loss of tolerance (TILT), and idiopathic environmental intolerance (IEI).

Approximately three percent of Canadians have been diagnosed with ES. It affects men, women, and children of all ages, but the prevalence increases with age, and 60 to 80 percent of those diagnosed are women.

Caroline’s story illustrates how ES can develop and how it can affect a person’s life:

Last winter, Caroline and her husband renovated their home, installing new carpet, painting the walls, and varnishing the woodwork. They didn’t open the windows much as they didn’t want to waste energy. During the renovations, Caroline became ill with flu-like symptoms, headache and nausea. After the renovations were completed, she continued to feel tired all the time, and to experience headaches, nausea, and occasional joint and muscle pain.

A few weeks later, Caroline noticed she had a stronger sense of smell than others, and that her symptoms were worse whenever she smelled perfumes, odours from cleaning products and their new furniture. She also began to feel dull, groggy and “spacey” when she came into contact with these products.

She stopped using scented cleaning and personal care products at home. However, it became more difficult for her at work, as others in her office wore perfumes. She developed headaches, had difficulty concentrating and often had to leave her workspace to feel better. Her symptoms would improve once she stepped outside for at least 20 minutes. However, her boss started to complain about her frequent breaks and Caroline felt increasingly stressed, as she was now also worried about losing her job.

She sought help from her family doctor, who referred her to several specialists over the course of many months: a neurologist, a gastroenterologist and a rheumatologist. Each doctor noted a few abnormal results from her physical and laboratory tests, but none could diagnose the problem. One doctor wondered if it might be “her nerves.” Caroline was finding it more and more difficult to cope, was getting more and more frustrated with the lack of progress in addressing her health problem, and began to feel depressed.



People with environmental sensitivities (ES) often visit several doctors before being diagnosed with the condition. Patients with ES are more likely to:

  • feel dull or groggy

  • have difficulty concentrating

  • feel ‘spacey’

  • have a heightened sense of smell


Source: Women’s College Hospital, Environmental Health Clinic, Toronto, Ontario - 2022

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Gisèle coaches clients living with fibromyalgia, multiple chemical and environmental sensitivities,

myalgic encephalomyelitis / chronic fatigue syndrome, and long-Covid

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