Old TVs used cathode ray tubes (CRT) to display image. These required a high voltage to make the picture, but since the picture was seen from a long distance, this went well. Then the came the need to watch computer screens also with the same CRT's, but smaller screens. These screens were viewed at a distance of 20 - 50 cm. Some people now got discomfort and rash. Was it the high voltage, strong magnetic field? Several installed negative ion generators to reduce the inconvenience. Was the ion generator helping to reduce the effect of the corona effect in the data terminal? Later we got flat screens for both TV and data terminals, so as a problem, this is now well forgotten, and let us now hope we are not getting more problems in the future.