Electrosensitivity. Wifi is a form of radiofrequency radiation that is known to cause a variety of symptoms including headache, difficulty concentrating and insomnia in a certain percentage of people. See http://www. Townsendletter. Com/july2007/wifi0707.Htm it is estimated 2-3% of people suffer from hypersensitivity to electromagnetic fields from wifi, cell towers etc. More info at http://www. Electrosensitivity. Org/.