Pediculicide

Pediculicides are substances used to treat lice (Pediculus humanus capitus).

Chemical treatments

Today, insecticides used for the treatment of head lice include organochlorines (lindane), organophosphates (malathion), carbamates (carbaryl), pyrethrins (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. Originally approved for onchocerciasis and strongyloidiasis, Ivermectin is now approved by the FDA for pediculosis.

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. [2] They are more acceptable to some parents who are concerned with the use of chemical pediculicides. Several plant products such as aniseed, citronella, coconut, neem and tea tree oils 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 animals, 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-foaming 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 on 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 proteases can have insecticidal effects. This process works through using naturally occurring enzymes similar to those within the insects themselves. These proteolytic 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

Dimethicone 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.

Accelerated Nano X-ray tomography of headlice treated with Silcap(4% dimethicone/96% mineral oil) ([1]). After 15 min the lice and nits are suffocated and dry out. Courtesy of Oystershell NV & University of Ghent

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."

Gasoline/Kerosene

The use of kerosene or gasoline for prevention or treatment of lice is 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. irritation 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.

Alcohol

Common rubbing alcohol, when applied to the head, has been known to kill both the adult lice and the eggs. Ethanol (ethyl alcohol, common alcohol) is toxic to arthropods including lice and an external application of it is harmless to humans. 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 increasing 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 one second, or a mixture of ethanol and the everyday hair conditioner can be made. 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, or it can be toxic to death if consumed.

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.