Most of the testing that's been done has shown that "electro-sensitives" confidently report the symptoms when they know the electricity is on, and the symptoms abate when they know that the electricity is off. In double-blind studies, however, they report they symptoms no more frequently than random chance. In short, testing has not yet supported claims of electro-sensitivity.
I also have a friend who did extensive study in this area in the 90s, and she found that the levels of electromagnetic "leakage" (my term, not hers) at power stations and under power lines is insufficient to generate the symptoms as claimed.
A more compelling explanation IMO is that these sites also feature other potentially deleterious factors, such as residences located near power lines and by high-volume traffic routes (resulting in heavier volumes of pollution). or residences near sub-stations with toxic substances on-site or leeching into the soil over time (and contaminating ground water, etc.).
In any case, if someone experiences mysterious symptoms that they attribute to some environmental factor, they should quickly seek a professional diagnosis rather than relying on Dr. Google. The symptoms may indicate a treatable condition or, more urgently, a serious condition requiring prompt intervention.
"Chemosensitivity" is kind of vague, by the way. "Sensitive" how? And to which chemicals? It's ok as a broadbrush description, but as a diagnosis it's about as nebulous as "pain somewhere in the body." Greater specificity would benefit both the sufferer and the researcher.
For that matter, I'm not sure that it's useful to group "chemosensitivity" together with "electro-sensitivity" either, since they would presumably operate by wildly different mechanisms, even if the reported symptoms are broadly similar. It would be like lumping a throat-closing peanut allergy with a trachea blocked by a poorly chewed piece of cheese; both will seal off the airway, but the cause and treatment of each is very different.
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