With 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:
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.
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.
There are three different treatment options. Not all involve drugs.
- 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.
- Oral medications are prescription products, used in the case of very resistant lice, or when other treatments fail. They are rarely used.
- Insecticides – Insecticides are the preferred treatment option for lice, because of the failure rates with wet combing. Insecticides kill live lice and nits.
“Alternative” and “Natural” methods for Lice
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.
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 schematic that schools can follow.
- 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
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.