Uniform classification of medical conditions is important because it encourages international scientific study and sharing of results.

It creates the basis for the assignment of codes in health care systems for provision of insured diagnostic and treatment services, and it can point in the direction of the primary necessary treatment approaches.

At present, in Canada, there is no diagnostic code for Multiple Chemical Sensitivities, despite the rapidly accumulating evidence and the fact that, according to Statistics Canada, approximately 3% of Canadians have been diagnosed with the disorder, which commonly overlaps with Chronic Fatigue Syndrome and Fibromyalgia.

The World Health Organization ("WHO") is the global standard-setter for assessing and classifying health problems. It is the most important reference for physicians, governments and courts alike around the world.

Under its International Classification of Diseases-10 ("ICD-10") the WHO classifies hypersensitivity (also known in Canada as environmental sensitivities or multiple chemical sensitivities) under Chapter 19 “(injuries, poisonings and certain other consequences of toxic causes)”. Other complex chronic conditions commonly overlapping with hypersensitivity are myalgic encephalomyelitis/chronic fatigue syndrome, classified in Chapter 6 (diseases of the nervous system) and fibromyalgia (FM), classified in chapter 13 (diseases of the musculoskeletal system and connective tissue). It is noteworthy that the WHO does not allocate any of these three conditions to Chapter 5 (mental and behavioral disturbances).

ICD-10 is used in many countries of the world, including Germany, where it is called ICD-10-GM (GM= “German modification”). The German Institute of Medicine, Documentation and Information Section, has confirmed that the above classifications are used in Germany, and that it is “assumed that the above mentioned diseases are uniformly classified in other states” (countries).