What Head Lice Are
Head lice are parasitic insects that cause itchy scalp in humans. Predominately found in children aged 3-11, head lice are notorious for rapidly spreading from host to host. They are found worldwide in both developed and emerging countries and but not more commonly found in poorer areas or on people with poor hygiene. Contrary to popular belief, head lice prefer clean hair and will often leave dirty, oily scalps for ones that are cleaner and therefore easier to get a blood meal from.
Head lice have been evolving with their human hosts for thousands of years and in many places around the world have developed a formidable resistance to the harsh chemical treatments often used to control them. Currently, 20% resistance to synergized pyrethroids, (ie. permethrin/piperonyl butoxide) has been reported in areas all over the globe. They are able to do this in part because when threatened can roll into a protective ball and go into a stasis, appearing dead for up to several hours.