Pediculicide
Encyclopedia
Pediculicides are substances used to treat lice
(Pediculus humanus
capitus).
), organophosphates (malathion
), carbamate
s (carbaryl
), pyrethrin
s (pyrethrum
), and pyrethroids (permethrin
, phenothrin
, bio-allethrin).
The only agents approved by the FDA for treatment of pediculosis are lindane and malathion.
Laboratory and clinical studies found that many of the pediculicides in the market are either not fully effective or are ineffective when they are used according to the instructions.
Pediculicides may rapidly lose their efficacy because of the development of resistance. Resistance of head lice to insecticides such as lindane, malathion, phenothrin and permethrin has been reported.
Ivermectin (which can be given orally) has been shown to reduce levels of louse infestation. Ivermectin is not approved by the FDA for pediculosis, though it is approved for onchocerciasis
and strongyloidiasis
.
, neem
and tea tree oil
s offer promise for new compounds to treat head lice infestation. However, the number of clinical studies is very limited, and most have methodological problems such as lack of a comparison group. Plain vaseline
also works and is non-harmful, though messy: like all insects, lice need to breathe, and smothering hair with vaseline or other oily/fatty substances (like the aforementioned plant oils) for several hours will asphyxiate them. Removing the oily substance itself can be somewhat difficult; in such a case a highly-foam
ing soap
will be needed. Vinegar is also effective and safe in the treatment of pediculosis. Hair is drenched in warm vinegar, and then a shower cap is put in order to suffocate adult lice and erode egg walls (rendering them unviable). The cap should be worn overnight or at least for six hours.
enzyme
s can have insecticidal effects. This process works through using naturally occurring enzymes similar to those within the insects themselves. These protease enzymes cause the insect to hatch and molt prematurely, destroying the creature's exoskeleton. These enzymes are similar to those found in meat tenderizers and digestive aids. The benefits of this type of treatment is that the lice do not develop resistance and these products are less toxic.
is a silicone oil, which coats and smothers the lice causing their death either by suffocation or dehydration. Most dimethicone lotions do not kill nits because the nits have only one breathing orifice, the operculum
, so the dimethicone has less access there. Therefore most treatments should be repeated after 7–10 days to kill any lice that hatch from the eggs or to treat reinfection by family members or class mates . Combination lotions and foams exist (Silcap, manufactured by Oystershell NV
) that have an immediate effect on nits (15 min, 96% mortality) by combining the rather viscous dimethicone with penetrating excipients that increase the delivery through the abdominal spiracles of adults and the operculum
of the nits. However, "Silcap is not yet available in the US. Import and distribution is still waiting for final FDA approval."
or gasoline
for prevention or treatment of lice is extremely dangerous due to the inherent fire hazard. Since 1989, there have been at least nine cases of children being severely burned during such attempts. These cases apparently occurred because, contrary to popular belief, it is the fumes of the gasoline, rather than the liquid itself, that are flammable. These fumes can ignite due to the presence of even a small spark or open flame - such as those caused by electrical appliances, cigarette lighters, or pilot lights in stoves and water heaters. The use of gasoline to treat lice also carries a high risk of dermatitis
(i.e. irration of the scalp).
Before gasoline (Petrol)
was used as fuel, it was sold in small bottles as a treatment against lice and their eggs. At that time, the word Petrol was a trade name.
, when applied to the head, has been known to kill both the adult lice and the eggs. Alcohol can be used as a remedy for pediculosis either by using a fine comb and dipping it in alcohol before combing, which is simply a way to increase the effectiveness of combing by rising the chances of killing any lice that the comb misses, or by soaking the head in a large quantity of alcohol and leaving it for a while, either with or without some means to stop the alcohol from evaporating, such as a shower cap
. Alcohol use, however, implies certain risks: the scalp can suffer irritations, for example, or it could get into the eyes and cause severe pain and discomfort.
Pediculosis
Pediculosis is an infestation of lice — blood-feeding ectoparasitic insects of the order Phthiraptera. The condition can occur in almost any species of warm-blooded animal , including humans...
(Pediculus humanus
Pediculus humanus
Pediculus humanus is a species of lice that infects humans. It comprises two subspecies:*Pediculus humanus humanus Linnaeus, 1758 – the body louse*Pediculus humanus capitis De Geer, 1767 – the head louse...
capitus).
Chemical treatments
Today, insecticides used for the treatment of head lice include organochlorines (lindaneLindane
Lindane, also known as gamma-hexachlorocyclohexane, , gammaxene, Gammallin and erroneously known as benzene hexachloride , is an organochlorine chemical variant of hexachlorocyclohexane that has been used both as an agricultural insecticide and as a pharmaceutical treatment for lice and...
), organophosphates (malathion
Malathion
Malathion is an organophosphate parasympathomimetic which binds irreversibly to cholinesterase. Malathion is an insecticide of relatively low human toxicity, however one recent study has shown that children with higher levels of organophosphate pesticide metabolites in their urine are more likely...
), carbamate
Carbamate
Carbamates are organic compounds derived from carbamic acid . A carbamate group, carbamate ester, and carbamic acids are functional groups that are inter-related structurally and often are interconverted chemically. Carbamate esters are also called urethanes.-Synthesis:Carbamic acids are derived...
s (carbaryl
Carbaryl
Carbaryl is a chemical in the carbamate family used chiefly as an insecticide. It is a white crystalline solid commonly sold under the brand name Sevin, a trademark of the Bayer Company. Union Carbide discovered carbaryl and introduced it commercially in 1958...
), pyrethrin
Pyrethrin
The pyrethrins are a pair of natural organic compounds that have potent insecticidal activity. Pyrethrins are neurotoxins that attack the nervous systems of all insects. When present in amounts not fatal to insects, they still appear to have an insect repellent effect. Pyrethrins are gradually...
s (pyrethrum
Pyrethrum
Pyrethrum refers to several Old World plants of the genus Chrysanthemum which are cultivated as ornamentals for their showy flower heads. Pyrethrum is also the name of a natural insecticide made from the dried flower heads of C. cinerariifolium and C...
), and pyrethroids (permethrin
Permethrin
Permethrin is a common synthetic chemical, widely used as an insecticide, acaricide, and insect repellent. It belongs to the family of synthetic chemicals called pyrethroids and functions as a neurotoxin, affecting neuron membranes by prolonging sodium channel activation. It is not known to...
, phenothrin
Phenothrin
Phenothrin, also called sumithrin, is a synthetic pyrethroid that kills adult fleas and ticks. It has also been used to kill head lice in humans...
, bio-allethrin).
The only agents approved by the FDA for treatment of pediculosis are lindane and malathion.
Laboratory and clinical studies found that many of the pediculicides in the market are either not fully effective or are ineffective when they are used according to the instructions.
Pediculicides may rapidly lose their efficacy because of the development of resistance. Resistance of head lice to insecticides such as lindane, malathion, phenothrin and permethrin has been reported.
Ivermectin (which can be given orally) has been shown to reduce levels of louse infestation. Ivermectin is not approved by the FDA for pediculosis, though it is approved for onchocerciasis
Onchocerciasis
Onchocerciasis , also known as river blindness and Robles' disease, is a parasitic disease caused by infection by Onchocerca volvulus, a nematode . Onchocerciasis is the world's second-leading infectious cause of blindness. It is not the nematode, but its endosymbiont, Wolbachia pipientis, that...
and strongyloidiasis
Strongyloidiasis
Strongyloidiasis is a human parasitic disease caused by the nematode Strongyloides stercoralis, or sometimes S. fülleborni. It can cause a number of symptoms in people, principally skin symptoms, abdominal pain, diarrhea and weight loss...
.
Natural products
Natural products tested clinically and found to be safe and effective could be very important in the control of head lice, as the complexity of the active ingredients may prevent the rapid development of resistance. They are more acceptable to some parents who are concerned with the use of chemical pediculicides. Several plant products such as aniseed, coconutCoconut
The coconut palm, Cocos nucifera, is a member of the family Arecaceae . It is the only accepted species in the genus Cocos. The term coconut can refer to the entire coconut palm, the seed, or the fruit, which is not a botanical nut. The spelling cocoanut is an old-fashioned form of the word...
, neem
Neem
Azadirachta indica is a tree in the mahogany family Meliaceae. It is one of two species in the genus Azadirachta, and is native to India growing in tropical and semi-tropical regions. Its fruits and seeds are the source of neem oil...
and tea tree oil
Tea tree oil
Tea tree oil, or melaleuca oil, is a pale yellow colour to nearly clear essential oil with a fresh camphoraceous odor. It is taken from the leaves of the Melaleuca alternifolia, which is native to the northeast coast of New South Wales, Australia...
s offer promise for new compounds to treat head lice infestation. However, the number of clinical studies is very limited, and most have methodological problems such as lack of a comparison group. Plain vaseline
Vaseline
Vaseline is a brand of petroleum jelly based products owned by Anglo-Dutch company Unilever. Products include plain petroleum jelly and a selection of skin creams, soaps, lotions, cleansers, deodorants and personal lubricants....
also works and is non-harmful, though messy: like all insects, lice need to breathe, and smothering hair with vaseline or other oily/fatty substances (like the aforementioned plant oils) for several hours will asphyxiate them. Removing the oily substance itself can be somewhat difficult; in such a case a highly-foam
Foam
-Definition:A foam is a substance that is formed by trapping gas in a liquid or solid in a divided form, i.e. by forming gas regions inside liquid regions, leading to different kinds of dispersed media...
ing soap
Soap
In chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...
will be needed. Vinegar is also effective and safe in the treatment of pediculosis. Hair is drenched in warm vinegar, and then a shower cap is put in order to suffocate adult lice and erode egg walls (rendering them unviable). The cap should be worn overnight or at least for six hours.
Enzyme-based products
Certain proteaseProtease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s can have insecticidal effects. This process works through using naturally occurring enzymes similar to those within the insects themselves. These protease enzymes cause the insect to hatch and molt prematurely, destroying the creature's exoskeleton. These enzymes are similar to those found in meat tenderizers and digestive aids. The benefits of this type of treatment is that the lice do not develop resistance and these products are less toxic.
Silicone-based lotions
DimethiconePolydimethylsiloxane
Polydimethylsiloxane belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, and is particularly known for its unusual rheological properties. PDMS is optically clear, and, in general, is...
is a silicone oil, which coats and smothers the lice causing their death either by suffocation or dehydration. Most dimethicone lotions do not kill nits because the nits have only one breathing orifice, the operculum
Operculum
Operculum may refer to:*Operculum , a stiff structure resembling a lid or a small door that opens and closes**Operculum , a lid on the shell of some gastropods**Operculum , a lid on the orifice of some bryozoans...
, so the dimethicone has less access there. Therefore most treatments should be repeated after 7–10 days to kill any lice that hatch from the eggs or to treat reinfection by family members or class mates . Combination lotions and foams exist (Silcap, manufactured by Oystershell NV
Oystershell NV
Oystershell NV is a Belgian commercial research institute that investigates and develops new medicinal products for over the counter use.- History :...
) that have an immediate effect on nits (15 min, 96% mortality) by combining the rather viscous dimethicone with penetrating excipients that increase the delivery through the abdominal spiracles of adults and the operculum
Operculum
Operculum may refer to:*Operculum , a stiff structure resembling a lid or a small door that opens and closes**Operculum , a lid on the shell of some gastropods**Operculum , a lid on the orifice of some bryozoans...
of the nits. However, "Silcap is not yet available in the US. Import and distribution is still waiting for final FDA approval."
Gasoline/kerosene (not recommended)
The use of keroseneKerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
or gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
for prevention or treatment of lice is extremely dangerous due to the inherent fire hazard. Since 1989, there have been at least nine cases of children being severely burned during such attempts. These cases apparently occurred because, contrary to popular belief, it is the fumes of the gasoline, rather than the liquid itself, that are flammable. These fumes can ignite due to the presence of even a small spark or open flame - such as those caused by electrical appliances, cigarette lighters, or pilot lights in stoves and water heaters. The use of gasoline to treat lice also carries a high risk of dermatitis
Dermatitis
-Etymology:Dermatitis derives from Greek derma "skin" + -itis "inflammation" and genetic disorder.-Terminology:There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term may describe eczema, which is also called...
(i.e. irration of the scalp).
Before gasoline (Petrol)
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
was used as fuel, it was sold in small bottles as a treatment against lice and their eggs. At that time, the word Petrol was a trade name.
Alcohol
Common rubbing alcoholRubbing alcohol
Rubbing alcohol, USP / B.P. is a liquid prepared and used primarily for topical application. It is prepared from a special denatured alcohol solution and contains 97.5-100% by volume of pure, concentrated ethanol or isopropyl alcohol...
, when applied to the head, has been known to kill both the adult lice and the eggs. Alcohol can be used as a remedy for pediculosis either by using a fine comb and dipping it in alcohol before combing, which is simply a way to increase the effectiveness of combing by rising the chances of killing any lice that the comb misses, or by soaking the head in a large quantity of alcohol and leaving it for a while, either with or without some means to stop the alcohol from evaporating, such as a shower cap
Shower cap
A shower cap is a cap worn while showering or bathing, to protect hair from becoming wet.Many are produced by joining two layers of fabric together in order to make the shower cap not only waterproof but aesthetic also. However, simpler ones are purely made from one layer of a waterproof material,...
. Alcohol use, however, implies certain risks: the scalp can suffer irritations, for example, or it could get into the eyes and cause severe pain and discomfort.
Research
A number of promising compounds are currently in development for the treatment of head lice. Approval of any of these products may make it much easier to treat head lice in the future.- Summers Laboratories is developing a benzyl alcohol-based treatment that kills by asphyxiation (Summer's Non-pesticide Lice Asphyxiator). This product is a water-soluble gel similar in consistency to a hair conditioner. It consists of a mixture of dermatological and cosmetic ingredients. The active ingredient is benzyl alcohol. The product was acquired by Sciele Pharma for distribution in the United States, Canada, and Mexico. The product was recently approved by the FDA and is being marketed under the brand name Ulesfia.
- ParaPRO is developing a crème rinse containing a novel biologically derived pesticide, Spinosad. The product, tentatively branded NatrOVA, is currently being tested in FDA approved clinical trials.