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Paper text:
each species of lice dwell in a particular host and a particular part of body 1 .
the female louse produces about 130 eggs ( nits ) in its life . after about 9 days ,
the nymph molts several times over the course of 15 days and becomes an adult louse 3 . away from host ,
mature lice survive just for 3 days , but this survival time is about 10 days for nits 2 , 4 .
lice spread from person to person when people 's heads touch or after sharing things such as hats , combs , clothing , headbands , brushes , or barrettes 4 , 5 , 6 .
control of this insect worldwide depends on the repeated or continued applications of pyrethroids ( permethrin ) , organophosphates ( malathion ) , carbamate ( carbaryl ) , organochlorine pesticides ( lindane ) , and in some countries ivermectin , benzyl alcohol ( ulesfia ) , and spinosad ( natroba ) 7 , 8 .
resistance to the common pediculicides may have contributed to the recent surge in head lice infestations 4 , 9 .
although pediculus humanus capitis ( head lice ) is not an important vector of microorganisms , it is a major social and economic concern in north america and worldwide 10
. infestation with head lice has been a chronic problem throughout the world for thousands of years , with an estimated 612 million cases of pediculosis occurring each year in the united states alone , most of which affect girls 1 , 11
. the annual cost of head lice in the united states may be as high as 1 billion $ because of costs for treatment , appointments with a provider , prescription medications , time spent by school nurses to inspect students , and time of work for caregivers who must stay home with their children during the infestation 12 .
recently , we were confronted with some permethrin  resistant pediculosis in a large family .
lice were present just on the head , and no lice were found in body inspection .
all of the patients of the family had already been treated by permethrin with no satisfactory result .
patients had just primary clinical signs of itching , and there were no other clinical or biological signs .
the second treatment of choice for human pediculosis is malathion , but because of poisoning probability in children , attempts were made to find a replacement for malathion . ultimately , ethanol was chosen and applied to the hair of the family members .
after ethanol spraying , a nylon bag was used to cover the patient 's hair .
three days after treatment , all patients were considered completely treated , and there were no lice and clinical signs of infestation .
contrary to the first treatment with permethrin , 3 days after alcohol application there was no live nit or louse on the heads of patients , all of the patients were satisfied , and they had no itching or other clinical signs on the head . in treatment of infective diseases , it is important to consider safety , efficacy , availability , expense , and ease of application 7 .
permethrin , malathion , and lindane are usual insecticides for treatment of head lice in the world 7 . in treatment failure with pyrethrin or permethrin , malathion is the second treatment of choice .
orally administered ivermectin has been reported to be efficacious , but it is not currently a us food and drug administration  approved pediculicide 7 , 13 .
it is indicated for the treatment of head lice in patients aged 6 months and older 14 .
benzyl alcohol 5% lotion ( ulesfia ) was approved in 2009 by the fda for the treatment of head lice in patients aged 6 months and older 15 .
suffocating  lice because it prevents the closing of the respiratory spiracles via obstruction , leading to asphyxiation .
spinosad 0.9% topical suspension ( natroba ) is a new pediculicide that was approved in january 2011 for treatment in patients aged 4 years and older .
although the suspension has been shown to be effective in patients as young as 6 months of age , systemic safety has not been evaluated for subjects younger than 4 years 16 .
many researches have been carried out for finding an effective and safe treatment for head lice .
for example , plant oils have been suggested as an alternative source of materials for insect control because they constitute a potential source of bioactive chemicals and are commonly used as fragrances and as flavoring agents for foods and beverages 17 , 18 , 19 , but till now , an effective commercial result has not been found .
insecticides are usually applied in very low dosage , about 1% , because they have a narrow safety border .
also , some of the treatments , for example , permethrin in treatment recommended dosage has a slight ovicidal effect that increases the probability of resistance occurrence . on the other hand , increasing the dosage of drug can cause poisoning in patients .
lindane is effective on eggs of lice , but lindane resistance among head lice has been reported in the united kingdom , the netherlands , panama , and the united states 4 , 20 , 21 .
easy absorption of lindane to skin can cause neurotoxicity and anemia in patients 22 , 23 , 24 .
for this reason , this treatment should be applied with extreme caution in patients with a history of seizure and in hiv infected patients 24 , 25 , 26 .
other side effects of lindan are mild edema , pruritus , stinging , burning , rash , erythema , and tingling 6 .
use of malathion in patients younger than 6 years is not recommended , and its use is contraindicated for neonates and infants because of increased permeability of the scalp 29 .
ivermectin , benzyl alcohol ( ulesfia ) , and spinosad ( natroba ) are new approved drugs , but they are not available for human use in all countries . benzyl alcohol can be used in patients aged 6 months , but it does not have ovicidal activity 15 . also , the cost of new treatments ( ivermectin , benzyl alcohol , and spinosad ) is much greater than that of old treatments 30 .
generally , the majority of new and old mentioned treatments have resistant probability problem in low dosage and poisoning probability problem in high dosage .
another property of insecticides is poison durability . for treatment of many of the external arthropod infestations , especially in animals ,
a chemical poison with high residual protection is a good and necessary property of pesticide ; but in head lice infestation , this is not necessary or good property because durability of the poison can aggravate the risk of poisoning especially in children .
ethanol , which is commonly called drinking alcohol , has many good properties regarding the efficacy , safety , cheapness , availability , patient preference , and ease of application features that are important factors for treatment selection .
ethanol has very low risk of poisoning occurrence because it evaporates rapidly and its pharmaceutical residues are very low .
so this treatment can be applied to children up to 3 years old with exact monitoring till alcohol evaporation .
although some side effects , especially carcinogenicity , have been expressed for ethanol 33 , topical usage of ethanol once or twice could not provoke such problems
. while many kinds of alcoholic drinks are available in markets , alcohol is cheaper than other treatments and can be the treatment of choice for head lice in epidemic conditions or outbreaks of head lice infestation .
key clinical messagehead lice ( pediculus humanus capitis ) infestation is an important disease worldwide , especially in children under 11 years old . 
 permethrin is the most common insecticide for treatment of human pediculosis , but nowadays resistance to permethrin and other pyrethroids has caused many treatment failures . 
 the second treatment of choice is malathion .