lice, head

Head lice (pediculosis capitis) is an infestation of the scalp and hair with, well, lice. They are small but in contrast to the scabies mite can be easily seen with the naked eye. What people usually notice first is the nits, or little white egg cases the louse leaves glued to the hair shaft. The infestation is very common in the winter months among school age children. (They put their coats in the cloakroom and the lice crawl from coat to coat.)

Parents and teachers generally freak out at the thought of lice but they are a nuisance, not a plague. The head louse does not transmit any serious diseases. (It is doubtful they transmit any human diseases at all - that role is played by the body louse, a different critter.) Treatment of head lice is straightforward: kill the buggers and all their children. We once used lindane, an insecticide, on the scalp. It is still available, however this chemical does a poor job of killing the eggs (nits) and it has been associated in rare cases with brain toxicity in small children when greivously misapplied.

Prescription Ovide® (malathion) is significantly more effective than lindane or permethrin pediculicides such as Nix®. It has the disadvantage of being significantly more expensive than permethrin-based treatment, and because it is an organophosphate insecticide, there is at least some concern about safety for use on children under 6. Nix®, Rid®, or A-200 Pediculicide®, are permethrin pediculicides available without prescription.

To get a formerly louse-infested child back in school, you've got to generally get the nits out of the hair - not because of danger of infestation, but because the school usually has a rule of zero tolerance for nits, whether they are live eggs or just the "empties." For that you need either Step 2® nit removal system or plain distilled white vinegar - either one will dissolve the glue that keeps the nit on the hair shaft and allow you to more easily comb them out. You will need a special nit comb to do that. (By the way: remember that any nit more than 1/8 inch from the scalp on the hair shaft is EMPTY and not infective.)

Cleaning up the house is important for getting rid of head lice. This includes spraying the sofa cushions, washing the bedding, spraying any hats worn, boiling combs and brushes or throwing them away.

Resistance to permethrins and even malathion has become common in most parts of the country. Here are some other ways I have read about to kill these resistant lice:

  • Use a shower cap overnight and apply petroleum jelly to the entire scalp to smother the lice. Wash out in the morning - easier said than done. Repeat for three nights. An alternative to Vaseline¨ is olive oil. Use a nit comb before removing oil or vaseline. (If you use Vaseline¨, be aware it may take 7-10 days to shampoo all of it out of the hair.)
  • Have the pharmacist make a preparation of petroleum jelly and 6% sulfur. Use the same way as above. You will certainly get no arguments about the hair wash after that treatment.
  • Head lice resistant to standard anti-louse preparations can be eradicated by using oral trimethoprim/sulfa (Septra®, Bactrim®) for three days and repeating this treatment 7-10 days later. This regimen kills the gut bacteria of the louse and it cannot make essential B vitamins or lay fertile eggs.
    British Journal of Dermatology 1978 vol 98, pp 669-700
  • Ivermectin is an antiparasitic drug which also directly kills head lice when they feed on blood containing the medicine. Ivermectin is given in a single oral dose of 0.2 mg per kg of body weight; if the lice are still moving after 24 hours the dose is repeated. The nits must be removed manually - the drug obviously doesn't affect them.
    Pediatric Infectious Disease 17:923, Oct 1998
  • Always check the scalp for nits for up to three weeks after treatment. Remember that nits are most commonly found in the hair around the nape of the neck and behind the ears.

Sometimes, things that appear to be nits are not. In head louse outbreaks, teachers and school nurses may send home children with anything in the hair that remotely resembles a nit. Examination under magnification easily identifies these "pseudonits." These hair and scalp conditions (humorously referred to as zebras) that are sometimes confused with nits include

  • hair casts (peripilar keratin casts) are cylindrical "beads" of keratin that slide easily up and down the hair shaft (nits are glued solidly in place)
  • seborrhea or psoriasis scales
  • trichorrhexis nodosa is a condition of splintered, partially broken hair shafts; grayish-white nodules are seen on the hair shaft that look under magnification "like two paint brushes pushed together"
  • pili torti or "twisted hair," is a hair shaft malformation, more noticable in blondes
  • pili annulati is a rare condition in which the hair shaft contains hollow air pockets that can appear white in bright light and mimic nits

Now, to get even more information than you ever thought possible (and even stuff and gadgets like the LiceMeister® nit comb) hop to the National Pediculosis Association Homepage. Isn't the Internet grand!

I have read of a library louse that infests old decaying books and can get on humans. It is picked up, naturally, at the library and is killed by Nix but keeps coming back until someone thinks to check the library.

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