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Pediculus capitis (Head louse)

Life > Eukaryotes > Opisthokonta > Metazoa (animals) > Bilateria > Ecdysozoa > Panarthropoda > Tritocerebra > Phylum: Arthopoda > Mandibulata > Atelocerata > Panhexapoda > Hexapoda > Insecta (insects) > Dicondyla > Pterygota > Metapterygota > Neoptera > Eumetabola > Paraneoptera > Psocodea (booklice and lice) > Phthiraptera (lice)

Head lice - greatly magnified - in reality they are each about 2 to 3.7 mm long. [photo Hannes Mitchell ].

Head lice are usually found on the head but they can be found amongst hairs in other parts of the body. They are a common problem in schools, causing consternation to teachers and parents alike (see Treatment below). The closely related Body louse Pediculus humanus is only found on the body or in the attached clothing. Head lice like clean hair so infection by these insects is not necessarily to do with poor hygiene. Body lice on the other hand tend to be found on people who do not wash regularly.  The third species of louse commonly found on people is the crab louse Phthirus pubis which prefers the pubic region but which can also be found in the armpits, beard, eyebrows and eyelashes. 

The eggs (or 'nits') of head lice are attached to hairs and the nymphs which hatch from them resemble the adults except being smaller. Depending on temperature, it takes 2-4 weeks for the eggs to hatch, the nymphs to pass through three moults and the adults to reach sexual maturity. 

Treatment

There are three main approaches to treating head lice infestations.

  1. Insecticidal shampoo. Two main types of shampoos are available in South Africa. The cheaper (and most commonly used) of the two contains Gamma Benzine Hexachloride otherwise known as lindane. There have been a number of horror reports of lindane causing neurological problems and the National Pediculosis Association in the U.S.A. strongly recommends that it should not be used. If you do use a lindane-based shampoo, follow the instructions very carefully particularly with regard to how often you can apply it. The other shampoo, which is more expensive, contains permethrin which has a much better safety record than lindane.
  2. Combing. Combing the hair with a louse comb is regarded as a very effective method but it takes time and it is recommended that for children you keep them occupied with something interesting such as watching a good video. Plastic louse combs (which sometimes come with the shampoo you buy) are regarded as ineffective and a metal one should be used instead.
  3. Application of oils. There is good anecdotal evidence that application of certain long-chain oils to the hair are effective in removing lice infestations. Coconut-oil or olive-oil-based shampoo (or bar soap or pure oils) are recommended in combination with combing: go to New York Coalition for Alternatives to Pesticides for the best procedure for using this technique. Alternatively, you can make up the following recipe: 30 ml olive oil, 20 drops of tea tree oil, 10 drops rosemary oil, 10 drops lavender oil and 10 drops lemon oil. With this recipe, first test that there is no skin reaction by applying a little of this solution to the inside of the elbow and wait a few hours to see if there is any adverse reaction. Apply this solution to the hair and leave it there for an hour, then shampoo (the shampoo should not contain a conditioner because the conditioner coats the hair and may protect the nits). It might be necessary to repeat this process after a couple of days to eliminate the next batch of hatched lice and maybe again after that.

In addition to direct control of the lice on the scalp, you also need to wash clothing and linen that might be infected and dry it on high heat in a dryer. Vacuuming of carpets, sofas and chairs is regarded as an effective way of removing loose lice and nits. Combs and brushes need to be soaked in a hot ammonia solution (1 teaspoon amonia in two cups of hot water). Head lice cannot survive for more than a couple of days at room temperature without feeding on blood, and the nits (eggs) take about 8 days to develop. Isolating items for about 10 days at warm temperatures is therefore an effective way of ridding them of any stray lice or nits. Putting an item in a plastic bag in the sun would kill lice and nits because of the high temperatures. Freezing the items for about four days would also kill the lice and nits.

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Text by Hamish G. Robertson.


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