In 1909, a Director of the Pasteur Institute, Charles Nicolle, discovered that the excrement of body lice was responsible for spreading epidemic typhus, a potentially fatal disease back then, and for this discovery he received the Nobel Prize in 1928.
A vaccine against typhus was developed in the 1930’s and dichlorodiphenyltrichloroethane, better known as DDT, was introduced as a treatment for lice infestations. Obviously, DDT was later determined to be toxic to animals and to humans, but this is the first of many documented uses of harmful pesticides to treat those with a lice infestation.
During the winter of 1944-1945, various head lice treatment formulations (10% DDT, 20% natural pyrethrum and others) were tested and adopted by the US Army during WWII.
From the 1950’s - 1970’s, DDT "successfully" limited lice infestations. After 1977, lice cases began to resurface as lice became resistant to DDT treatments and new treatments with the chemical permethrin, became more widely used. Pyrethrum was later replaced by synthetic derivatives called pyrethroids, including d-phenothrin and permethrin. These pyrethroids were chemically modified to be more stable with respect to heat and light than natural pyrethrum, and pyrethroids are the most common ingredients in most over-the-counter insecticides currently marketed for the treatment of lice.
Lindane was introduced as a prescription only treatment, but immediately came under pressure from health organizations because of its low efficacy rate (30-50%) Many concerns over use of Lindane and possible overuse as well as its linkage to seizures due to it's potential neurotoxic effects has resulted in the American Academy of Pediatrics, the Medical Letter and the Stafford Report to recommend not using Lindane for the treatment of nits and lice. It is now banned in California and has been in the EU since 2007.
Malathion, a neurotoxic organophosphorus insecticide, was also introduced as a head lice remedy, but was later removed from the US market in 1990 because of problems caused by lengthy application times, flammability, and its' unpleasant smell, however was re-introduced in the US in 1999 as other treatments became less effective.
Resistance to malathion has been reported now for a number of years in several countries, including the US and is currently only available as a prescription treatment in the US.
Today, consumers quite possibly unknowingly still use treatments that contain pesticides and other toxic ingredients, even though they produce minimal success after repeated treatments and no active path to removing nits from the hair.
A number of Salons specializing in removing nits and lice have become popular, but their high costs make this option not available to everyone.