Got Lice? Use Science, Not Placebos

Pediculus_humanus_var_capitisWith the return to school earlier this month, we’re in prime lice season. I was recently forwarded a copy of a Toronto public school’s communication on head lice. Here’s an excerpt:

Oil & vinegar lice treatments do not kill live (unhatched) nits & have to be hand picked. It must be repeated daily until no nits (eggs) are found. Both light (hatched) and unhatched nits must be removed by hand (lice combs won’t pull all nits), and the hair needs to be checked daily for new nits.  As much as no-one wants to put chemicals in their child’s hair, in severe cases it might be advisable. Medicated shampoos and cream rinses have a residual effect, but daily nit picking is required. As well a second treatment with the same treatment in a week is required. Homeopathic treatments are available, but eggs must be picked daily. Teatree oil, as a shampoo or oil (massaged in the scalp) is said to be a preventative. However, if you already have nits or lice, it will not kill or remove them. Remember: One nit left on the hair will keep the cycle going.

This paragraph is so full of inaccurate information, it’s astonishing.  First a bit of background, then let’s examine the evidence supporting this school’s advice.

Lice are a common infestation that affect children, particularly in primary school. Pharmacists are pretty used to dealing with head lice. Lice treatments and combs fly off the shelves once school starts, and pharmacists dispense a lot of advice to distraught parents. Lice infestations can be self-treated and usually do not require a physician visit.

Head lice (Pediculosis humanus capitis) are insects that can infest human hair. It sounds horrible, but the medical effects are mainly limited to skin irritation and itching. The social implications and shame can be much more traumatic to children. Lice are highly prevalent – only the common cold is more common in children. It’s estimated that in a single year, about 1 in 4 children become infested with lice.

Lice is spread by playing closely together, and by sharing  headwear, towels, and beds. Lice cannot jump from head to head.

Female lice lay 7-10 eggs (“nits”) per day. Nits are small grey ovals that attach to the base of the hair follicle. They hatch about 7-10 days after birth.

Head lice infections are diagnosed when live lice are spotted. Nits without live lice does not mean infection, as nits can stay on the hair for months after an infection. To be clear – nits only is not an infection. Only 1 in 5 children with nits progress to an actual infestation. So there is no rationale to treat nits with medication – only when live lice are spotted is it necessary to treat an infestation. The best way to check the hair is with a lice comb.

Unless there is an infestation, as evidenced by live lice, nits do not have to be removed. Nits, without lice, does not mean an infestation, and does not require treatment.

Treatment Options

There are three different treatment options. Not all involve drugs.

  1. Wet combing is a drug-free method that involves wetting the hair and removing the lice through combing the hair with a lice comb repeatedly. Every single hair follicle must be checked and stripped of lice.  The hair can be pre-treated with conditioner, vinegar, even olive oil to lubricate the hair. Combing must be done ever 3-4 days for 2 weeks following the identification of any live lice. Wet combing is the preferred treatment in children less that 2 years old. In older children, wet combing, by itself, is not routinely recommended. And picking through the hair with fingers alone is not effective. A lice comb must be used.
  2. Oral medications are prescription products, used in the case of very resistant lice, or when other treatments fail. They are rarely used.
  3. Insecticides – Insecticides are the preferred treatment option for lice,  because of the failure rates with wet combing. Insecticides kill live lice and nits.
Products for lice treatment in Canada include Pronto Shampoo, R&C shampoo, Nix Creme Rinse, Kwellada P Creme Rinse, and Resultz. Resultz is unique is that it contains an alcohol, isopropyl myristate, that dissolves the lice exoskeleton. The other agents contain neurotoxins. Each product has its own advantages and disadvantages. There is no good evidence to show that any product is more effective than another, as comparative trials do not exist. In addition, there seems to be difference resistance patterns – so what works in one area may not work in another. Pharmacies and public health units may have advice about what works in a particular area.
All insecticide treatments should be repeated after 7-10 days, as no treatment is 100% effective. Daily nit picking, however, is not required, if a chemical treatment is used. However, some do so for cosmetic reasons, and some guidelines do recommended it to boost the odds of treatment success.

Treatment Protocol

If chemical treatments are used, there is no good evidence to show that nits need to be removed. It seems to be preferred more for cosmetic purposes. A lice comb (preferably metal) can be used to remove nits and dead lice. Lice combs are superior to using hands. The wet combing method required nit removal. If chemical methods are used, nits do not have to be removed.
If the wet combing (non-chemical) method is used, nits must be removed completely. If the wet combing method is used, the hair must be brushed and searched for lice every 3-4 days – daily is unnecessary.

“Alternative” and “Natural” methods for Lice

Whether a product is naturally occurring or not means nothing with respect to either safety or toxicity, but seems to reassure people that are reluctant to treat head lice with medicated products. R&C Shampoo contain pyrethrin (manufactured from chrysanthemum plants) and piperonyl butoxide which helps pyrethrin work more effectively.
A popular alternative product (misleadingly touted as a “chemical-free treatment”) is called Treemenda Lice Stop. It’s not free of chemicals, though – it contains ethanol, tea tree oil (main ingredient is terpinen-4-ol, an eye and skin irritant) and oil of oregano (main ingredient is carvacrol), which is claimed to heal just about everything, but with no evidence to support its use. There is no information to suggest that this product, or any other “natural” remedy is either safe or effective. The only effective component of Treemenda Lice Stop may be the lice comb it is packaged with.

Products like petroleum jelly, mayonnaise, and olive oil are promoted as “safe” treatments that suffocate lice. Laboratory studies have demonstrated that this approach does not kill live lice or nits, and so are prone to treatment failures and ongoing infestations. As noted above – you can treat lice without chemicals. But you must be diligent, and you must, must, must remove every louse with a lice comb – and you must do this every few days.

Homeopathy is a antiquated elaborate placebo system where the “treatment” has no active ingredient. Using homeopathy is like using the wet combing method – but you’re out $20 because you bought a bottle of magic water.  If you use this method, remember that the wet combing method is associated with more treatment failures, and the hair must be inspected and combed through every few days. Every single louse must be removed, every combing session. Because they have no active ingredient and no demonstrated efficacy, homeopathic products  have no role as a treatment option for lice.

Dealing with Infestations

  • There is no reason for children to be sent home from school if they have lice or nits. Until the infestation is treated, however, close head-to-head contact is discouraged. Children may return to school after the first treatment session. This is an excellent, evidence-based overview that schools should review.
  • When one family member is diagnosed with a lice infection, all family members should be inspected, and if necessary, treated at the same time.
  • There is no role for preventative treatment (e.g., tea tree oil), as it has not been demonstrated to have any effect.
  • Household cleaning can be limited to washing and drying (with heat) items like bed linens and hats. Furniture and carpets can be vacuumed, but chemical treatments are unnecessary. Non-washable items can be sealed in plastic bags for 2 weeks. See suggested readings below for more information.


Reevaluating the Toronto District School Board’s communication on lice, it fails decisively. The Board has fallen prey to pseudoscience (tacit endorsement of homeopathy), the naturalistic fallacy (reluctant positioning of chemical treatments) and a lack of understanding of infection control (regarding lice and nit removal). The Board does not understand the different treatment options, and give incorrect advice about managing infestations. It also creates unnecessary worry in parent by confusing the appearance of a nit, with the diagnosis of a lice infection.

The social stigma attached to lice infestations make managing fears as important as treatment. Lice infections are often misdiagnosed, and parents embrace all type of implausible or ineffective treatment. Unfortunately, with lice, there is no placebo effect, and so treatment failures due to ineffective products or improper techniques are common. Only through adopting science- and evidence-based methods can the infestation cycle be broken.  Pharmacies, when they sell implausible treatments (like homeopathy) or unproven treatments (like tea tree oil) only serve to frustrate parents, children, schools, and science-based health professionals.

And that’s about all you need to know of the science of treating lice infestations. Is your head itchy yet?

For More Information

Harvard School of Public Health – Head Lice Information
UpToDate Patient Information – Head Lice
Medline Plus – Head Lice


Mumcuoglu KY, Barker SC, Burgess IF et al. International guidelines for effective control of head louse infections. J Drugs Dermatol 2007; 409-14.

Goldstein AO, Goldstein BG. Head lice (Pediculosis capitis) In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2009.

Update on Head Lice. Quick Facts for Pharmacists. Drug Information and Research Centre, Ontario Pharmacists’ Association. 2007.

16 thoughts on “Got Lice? Use Science, Not Placebos

    • It’s not well known, but believed to be related to schools: the impact of close interaction with playmates, transfer from articles of clothing on hooks in cloak rooms, and shared headwear. This may explain why children aged 3-12 are most affected, with much less impact and infestation in older children.

  1. Prevention has been proven to work. A study done by Fairy Tales Hair Care proved that Rosemary Repel hair care does prevent head lice. It uses organic herbs such as rosemary, citronella, tea tree, lavender and geranium. You can see the actual lice staying away from it in a test on their site at The company sells to salons, pharmacies and online.

    • Hi, please post the link where the study was published. Seeing lice stay away from something does not mean that it actually prevents infestations under real-world conditions. At present, evidence-based treatment guidelines do not advocate or endorse any specific prevention approach other than physical measures.

      • Scott- you can visit their site and they have information on the study posted. They don’t claim to be 100% effective but when used properly and with parents being proactive and doing head checks, the rosemary and citronella have been proven to be highly effective. Hadassah University in Israel has a world renowned Dr. who researched and concluded that lice detest rosemary oil and that is their main ingredient.

      • I visited this site, and I still don’t see anywhere where this potion has been proven to be highly effective when used as recommended. Studies showing a kill rate (or “Knockdown”, as detailed) with direct application of the product to bedbugs can hardly be extrapolated to treatment of lice given that lice and bedbugs are two very different species with different habits, feeding patterns and habitats. Furthermore, a video of some lice crawling around in a petri dish may show promising results, but it’s not enough to comment on real-world efficacy. As such, a figure of 92% to represent efficacy is misleading, and the term “in-vitro efficacy study” is hilarious. If the company provided a copy of the original study that accurately illustrated the design and results, plus a follow-up study evaluating the product’s use in a representative patient population, THEN you could comment on the efficacy. Until then, this is yet another product being sold to unsuspecting, desperate parents under the guise of being “safe and natural”.

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  3. YUP!! Totally true. Lice is on a worldwide rampage, and its mission is to infest every child’s head. Our family just recently went through what we could call “lice hell” and finally found our way out. I wouldn’t wish it on anyone.

    I never heard of the “homeopathy” option. That’s a new one, but the schools are really the main way kids get them. I think 1st period teachers should inspect heads, instead of just waiting for the nurses.


  4. The research on essential oils is slow and financially not viable, unless chemical approximations of essential oils can be reproduced by pharmaceutical companies. Nonetheless, some research work with essential oils is finally coming onto the lab scene:


    2.Journal of Medical Entomology 43(5):889-895. 2006
    doi: 10.1603/0022-2585(2006)43[889:FARPOE]2.0.CO;2

    Fumigant and Repellent Properties of Essential Oils and Component Compounds Against Permethrin-Resistant Pediculus humanus capitis (Anoplura: Pediculidae) from Argentina

    The treatment using plant extracts is not perfect but nothing in biology is. Let us give these essential oils at least a few (20-30 perhaps) years in the analytical labs to catch up to conventional pharmaceuticals. In the end, we may find that a combination treatment of plant extracts and pharmaceutical solutions is the most effective strategy for killing off lice, as well as many other unwanted parasites. After all, lab formulations stay the same until their efficacy is shown to be waning, while living organisms, such as plants, are constantly evolving.

  5. The “homeopathy option” is real, and not a placebo. Here’s a link to a case from the 19th century, before all those nifty modern chemicals were invented:

    It won’t make much sense to anyone not a homeopath, but it does show how a case of head lice was cured by a single remedy. The remedy this homeopath used, however, is not necessarily the one your kid might need — it all depends on the symptoms the person is showing. There are other remedies appropriate to other symptoms. And what was treated was not so much the head lice as the patient’s susceptibility to developing such a severe case.

    To blow your mind even more, Scott, let me add that Pediculus capitis is actually used to make a homeopathic remedy, one that’s been used to cure vitiligo and cystitis. (Again, that does not mean it should be used for any case of vitiligo or cystitis; it all depends on the accompanying symptoms.)

    It may be human nature, but it’s not wise to display your own ignorance by deriding what you don’t understand or have the credentials to evaluate.

    • Two whole cases of eczema as “evidence” for the general treatment of lice. That’s epic. Unlike the thousands of people helped by those nifty modern chemicals… My mind is blown.

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