Electrical sensitivity (ES), also known as electrical hypersensitivity, produces symptoms in a patient when exposed to common levels of electromagnetic fields (EMF) from electrical sources in the environment such as power lines, motors, computers, and so on. ES patients often are also MCS sufferers. Other at-risk groups for developing ES seem to be CFS patients and those experiencing mercury toxicity from dental amalgams. Overexposure to EMF can bring on ES, independent of other illness. Some ES patients experience only one symptom when EMF exposed, but often more than one symptom is apparent. Electrical sensitivity is more well-known in Europe than the United States, due in part to Sweden's active support group, FEB, which has about 2,000 members.

Once a patient realizes that proximity to electrical sources is the triggering event that leads to their symptoms, they find EMF avoidance helpful for reducing reactions. Unfortunately, with the advent of increasing wireless technology, such as cellular phone service and paging systems, EMF avoidance is becoming very difficult for the sensitive, creating more suffering and leading to life-threatening consequences for the severely ill. The chemical sensitivity equivalent of this wireless technology might be aerial pesticide sprayings, a life-threatening event for many MCS patients.

In the past, if daily computer use at work caused symptoms, a cause-and-effect relationship could be determined by noticing that these symptoms abated evenings and weekends and intensified at work. It would become clear that the workplace, at least, was responsible for the development of the symptoms. However, it could instead be a "sick building" problem in the workplace due to chemical exposures.

For the newly ES, it will now be more difficult to pinpoint the cause of their symptoms if they are also reacting to the ambient EMF exposure from various wireless services. The new digital cellular is particularly troublesome for some ES; the previous analog cellular system, operating at a lower frequency, was much less of a problem.