Symptoms manifest themselves differently from person to person (Figure 1). The list of possible symp- toms is very long and is not exclusive to environmental sensitivities. In the same individual, symptoms vary depending on the trigger, the level or dose of exposure, as well the duration of the exposure. In general, symptoms resolve once triggers are avoided, but will reappear with another exposure. Symp- toms may take minutes, hours or days to resolve, even when the triggering agent has been removed. They may also appear within minutes, hours or several days after exposure to the triggering agent.
One low-level isolated exposure, for example, a person wearing perfume and sitting a couple of metres away from a person suffering from environmental sensitivities, could cause the latter to manifest symptoms such as headache, confusion, breathing difficulties or loss of balance.
An individual’s level of tolerance to exposure is variable with time. Thus, the more a person is exposed to triggering agents, the stronger the symptoms, and the more the person will develop sensitivities to other agents. When a person manages to reduce the level of global exposure, the tolerance to specific triggers sometimes increases, and the symptoms become less severe. Therefore, certain exposures can be tolerated in some instances, for a certain period of time, and then not be tolerated at other times. This makes understanding the condition difficult for those who are suffering and for the people around them.
We don’t know why certain people are more sensitive than others. There does seem to be an indivi- dual susceptibility involved (age, state of health, other illnesses), as well as a genetic predisposition to developing environmental sensitivities. It is important for sufferers to identify and avoid the agents that cause symptoms and to receive the care needed to recover and maintain good health. However, it does appear that people suffering from environmental sensitivities will be affected, to some degree, all their lives.