Treating head lice
Beth Nash, physicians editor, BestTreatments
BMJ Publishing Group, London WC1H 9JR bnash@bmjgroup.com

Description
Head lice are parasites that usually infest the scalps of school age children, although adults also get them. Lice attach their eggs to hair shafts near the scalp and lay five to six eggs a day. Lice never willingly leave the head; they stay close to the scalp for food, shelter, warmth, and moisture. They are most often found behind the ears and at the back of the neck. Hatched eggshells (nits) may be confused with dandruff. The mature louse is the size of a sesame seed and has six legs and hook-like claws that grasp the strand of hair tightly, making it difficult to dislodge. It feeds on the host's blood every three to six hours, which can cause scalp itching, though most cases are asymptomatic. The diagnosis of lice infestation can be made definitively only if living lice are present.
 
DR JEREMY BURGESS/SP

Treatments that are likely to work

Malathion
Malathion works as well as other agents used to kill lice. Malathion must be left on for at least eight hours for it to work. It is applied to dry hair until the scalp and hair are wet and thoroughly coated. If lice are found 7-10 days after treatment, treat again with the same or different medication. The alcohol in malathion lotion and the terpenoids may cause stinging. Malathion is considered safe in pregnancy or breastfeeding.

Lindane
Although lindane may work as well as other insecticide based agents, its use is limited by its potential neurotoxicity. It is applied, for only four minutes, to wet the hair and skin or scalp of the affected area and surrounding hairy areas. Treatment may be repeated after seven days if necessary. Lindane should be avoided in pregnancy and breastfeeding. If it must be used in pregnancy, it should only be used once.

Permethrin
Permethrin may work better than lindane, though most trials were done before permethrin was widely used and resistance to the drug developed. It is used as 1% creme rinse left on for 10 minutes. If the first application fails to kill the eggs (that is, if young hatching lice are found using a suitable detection comb) a second treatment is indicated, usually seven days after the first treatment. Undertreatment in this situation could contribute to the development of resistance to the drug. There is no role for a third application, as this will contribute to resistance and is not likely to be effective. Permethrin has not been studied in pregnancy.

Pyrethrins
Pyrethrins are used as a 0.33% shampoo or mousse, by applying enough to thoroughly wet the hair and leaving it on for 10 minutes. All pyrethrum products that conform to the US Food and Drug Administration criteria for use in humans require a second application after 7-10 days, to ensure treatment of lice emerging from eggs that have not been killed by the first application. Pyrethrins work as well as permethrin.

Treatments that need further study
Herbal treatments and aromatherapy
Herbal treatments (including tea tree oil) and aromatherapy are sometimes used to treat head lice. No studies have evaluated their efficacy or possible toxicity.

Mechanical removal of lice or viable louse eggs by combing
There is insufficient evidence to determine the efficacy of "bug busting" (wet combing with conditioner). Many combs have been developed for lice removal, but many that are used are inappropriate. There is little evidence to support the use of any combing method. In one trial, significantly more people treated with malathion than with bug busting had no lice at seven days (31/40 (78%) v 12/32 (38%)). A new study (which we have not yet added to the BestTreatments site) looked at permethrin creme rinse with and without combing; permethrin without combing was marginally more effective.1


Misconceptions about head lice: what does the research really show?  

There is no evidence to support the cleaning of sheets and clothing, or the treating of earphones, baseball helmets, and furniture with insecticide sprays.

Infection is spread between people only by relatively prolonged head to head contact; thus it is typically spread between people who know each other well. Lice seen on chairs, pillows, and hats are dead, sick, or elderly or are cast skins of lice—these cannot infect a person.

School based "no-nits" policies (banning children with nits until all nits are removed) do not make sense—less than 20% of school children with nits will go on to develop infestation within 14 days. About half of children sent home for head lice don't have them. Many public health experts believe that "no-nits" policies should be abandoned.

Treatment should not be started unless live lice are found. Nits are not a sign of active infestation with head lice.

Cutting hair, or tying it back, is not helpful and may increase the incidence of infestation by making it easier for lice to move off of and on to the scalp.

Head lice are probably more common in girls because girls are more likely to have close contacts during play—not because they have longer hair.

Head lice are harmless. If detached from their host they are vulnerable and effectively dead.

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This is an extract from BestTreatments, which provides a shared online information resource for patients and doctors, based on Clinical Evidence (www.clinicalevidence.com). More information about head lice, including references for this BMJ article, is at https://www.besttreatments.org/headlice
This extract from BestTreatments will remain available at bmj.com. The rest of the BestTreatments website (www.besttreatments.org) is currently available only to patients who are members of United Healthcare plans in the United States.


References

Meinking TL, Clineschmidt CM, Chen C, Kolber MA, Tipping RW, Furtek CI, Villar ME, Guzzo CA. An observer-blinded study of 1% permethrin creme rinse with and without adjunctive combing in patients with head lice. J Pediatr 2002 Nov;141: 665-70[CrossRef][ISI][Medline]


This article has been cited by other articles:

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I had lice once. As soon as I found out, my mother washed my hair with special shampoo that killed the lice and combed them out with a metal brush. Seemed to work fine for me  ;D!

I'm sorry to say, I have TONS of experience in this problem.  Living in South Florida, there are several "seasons" where the lice will spread.  Tropical/warm climates tend to have ideal conditions.  

With 3 school age children and 1 in day care, I combat these creatures quite often.  After spending what seems like millions of dollars on over-the-counter and prescription remedies, we still came up on the loosing end of the battle.  After repeated phone calls to the pediatrician, they finally suggested I try using mayonaise!!  She suggested getting cheap shower caps and leaving it on overnight.  What a mess but it is so much cheaper and it WORKED!!!!  I have since only kept it on the hair for 2 hours, instead of over night with the same success and happier sheets!  It also left the hair pretty conditioned and shiny.  Now, as soon as someone starts itchin' they get the mayonaise!!  

I haven't needed to use this yet this summer, I hope we're through with that cycle until Baby goes to school.....

I hope this helps someone!!

I got head lice only a year ago, at the age of 17 from babysitting. The Permethin treatments are crap because lice are so resistant. The only thing that really works is combing the lice out and avoiding reinfestation. It has to be done well by combing down both sides of the middle part, turning your head upside down and combing up, throwing all your hair to the left and combing and then to the right. On my waist length hair it would take at least an hour. Use lots of conditioner and then start with a wide tooth comb, then medium, then fine, then all the way to a tiny-toothed lice comb. You then need to spray your pillows and wash your clothes and hair accessories. You should put your hair up until you are sure that all your family and friends have been treated, and do not rest your head against any chair headrests in your home until you spray them.

Hi

I only got caught with it once and I used a blend of aromatherapy oils.  Without looking it up I can't remember exactly which ones they were although I believe they were tea tree, bergamot and ? one other.  I know it was mixed in with a carrier oil and left on for about an hour.  It definitely worked and all the family had the same treatment.

However I like the sound of using mayo - much easier.  :)