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What are Head Lice?

Head lice (pediculus humanus capitis) are small brown-coloured wingless insects with a flat body that ranges in length from 2 to 4 mm. Hatched from tiny off-whitish eggs - commonly referred to as nits - they are usually laid in the hair of humans. Nits are sometimes confused with dandruff, the difference being that nits attach very firmly to the shaft of the hair and resist removal, unlike dandruff which flakes off easily. Nits hatch after 7 to 10 days, take around 17 days to mature to adults, then live for up to 18 more days before dying. During this adult phase, the female head louse may lay up to 10 nits per day. Throughout its life, it will feed 3 to 4 times a day on the blood of its host.(1)

In a report published in 1998, researchers at James Cook University presented their findings on head lice infestation in school-aged children in Australia.(2) They concluded that the extent of infestation was of almost epidemic proportions in some schools. For instance, of 456 students examined in one urban school, 154 (33.7%) showed evidence of head lice, with 95 (21.0%) of these with an active infestation at the time of testing. Indeed, one class reported an incidence of 72% of students infested with the parasite. Other sources suggest that the problem is no less severe in New Zealand schools.

Importantly, infestation has nothing whatever to do with the grooming or general cleanliness of the individual. Head lice can survive equally as well in clean or dirty human hair and are spread primarily by direct head-to-head contact, less by shared brushes, combs, hats, ribbons, etc. Whilst head lice are not disease carriers, infections can set in from excessive scratching by the infested host.(1)

Head Lice and Swimming Pools

Whilst not common, transmission of head lice in a pool environment is possible, with the water as the actual vehicle of transmission.(3) Head lice pass from one individual to the next by direct person-to-person contact or cocontact with a hard surface, such as a towel or even a table top. Transmission via water requires that the nits be removed from one individual and float in the water until they are deposited onto another individual. The nits are not immediately killed by the sanitiser in the water, as they are highly resistant to chemical attack. This resistance explains why it is so difficult to get rid of head lice once they have attached to an individual's hair.

Treatment of Head Lice and Removal of Nits

There are two more common methods used for the treatment of head lice, namely using an over-the-counter pharmaceutical or "wet combing" using an appropriate medicated scalp conditioner. Most pharmaceutical treatments contain an insecticide (eg. maldison (malathion) or a pyrethrin) and are effective at killing both adult lice and nits. Wet combing is said to "stun" the head lice, permitting their removal and that of the nits. Other reported treatments include electrical combs, essential oils and enzymes. The Public Health SA web page however warns against using or handling electronic head lice combs by individuals who suffer from epilepsy, heart disease or have a pacemaker or other neurostimulator device fitted.(1) As always, seek medical advice immediately in the event that an individual reacts adversely to any treatment.

Note that it is not necessary to remove nits if they are dead (usually those eggs more than 1 cm from the scalp). Wetting hair with vinegar sometimes loosens nits, which can then be combed off with a head lice comb or picked out with the fingers. Note, too, that many treatments do not kill 100% of the nits, and even in cases of successful treatment, this does not preclude a person from being re-infested at a later date.(1)

Further information is available from your local council or health authority. All government health departments and many councils detail head lice incidence, reporting and treatment on their web sites.


1. "Head Lice and Nits" (www.dhs.sa.gov.au/pehs/topics/topic-headlice.htm), Department of Human Services, Adelaide, SA.
2. R. Speare and P.G. Buettner, "Head Lice in Pupils of a Primary School in Australia and Implications for Control", International Journal of Dermatology, 38 (1999) 285.
3. D. Rouse (Bio-Lab, Lawrenceville GA), Email message to G. O'Connell, 11 December 2001.

The above information is supplied by Bio-Lab and represents its best interpretation of available technical information at the time of preparation. The sole purpose is to supply factual information to Bio-Lab customers. It is not to be taken out of context nor used as support for any other claim not made herein.