Even thinking about head lice can cause you to scratch and itch! Head lice are very common in school-aged children and are a nightmare for parents. Pediculus humanus is a highly contagious mite that is responsible for causing head lice. The louse can only survive on humans. It is spread by direct head to head contact and contrary to popular belief, it cannot jump or fly.
The life cycle of Pediculus humanus involves the following steps:
- The egg is laid onto the hair shaft. Colloquially, the eggs are referred to as “nits”
- After about 7 days, the egg hatches and the louse emerges
- Between days 8 and 17, the louse moults 3 times (sheds off its outer coating)
- After the third moulting, the lice are classified as adult lice and are capable of reproducing
- At around day 19-20, the female louse lays the first egg. The first egg is laid 2 days post mating
- For the next 16 days, the female can then lay between 3 and 8 eggs per day (they can lay up to 100 eggs)
- The louse dies, after a life spanning about 35 days
The life cycle of the louse helps to determine the application of some of the treatments discussed later. If the louse is separated from the head, it dies within 24 hours.
Lice: the lice are 6 legged creatures, with each of the 6 legs ending in a claw. They are normally a white or grey colour and are about 2-4mm in size. The lice are most commonly found on the hair shaft itself, migrating towards the scalp so that they can feed off the blood. They are often found behind the ears and in the nape of the neck.
Eggs: eggs have different appearances depending on the state of the egg. Eggs that have been recently laid tend to be yellowish-white in colour and are found on the shaft of the hair close to the scalp. These eggs may be mistaken for dandruff, but a key difference is that unlike dandruff, the egg will not brush off easily. Eggs that have hatched resemble small boiled eggs and dead eggs have a wrinkled, squashed appearance.
Signs and Symptoms
- Head lice can be very itchy and vigorous, repeated scratching of the head may be a good indication of head lice
- Sometimes, especially behind the ears and at the junction of the hairline and the neck, red bite marks with or without scratch marks may also be observed
- With constant scratching, the skin can break, which then provides the opportunity for a secondary infection to occur
Head lice can be removed manually using conditioner and combing the hair. This is also a method recommended to detect lice in the first place. The conditioner is necessary because it closes over the hole that the louse breathes through. Although this doesn’t kill lice, it will stun them and stop them from moving rapidly through the hair so that the lice can be more readily brushed out. It is particularly important to ensure that there is good coverage of the hair close to the scalp, as this is where the lice are most likely to be found. In early stages of infestation especially, the lice tend to aggregate on the crown of the head. If your child has long, thick hair, it might be easiest to divide the hair into manageable sections to treat with the conditioner, rather than attempting to coat and comb the entire head at once.
After you have applied the conditioner to the hair, use a fine comb, such as the special head lice combs available at pharmacies, to comb a thin section several times. Wipe the comb onto a towel, tissue or paper towel to see if the lice have come out of the hair. Continue this method throughout the whole head until there are no longer any lice or eggs coming off the comb. Tie back long hair after the process is finished. It is advisable to repeat this process at least every second day for a fortnight. The conditioner and comb method may be ceased when no lice have been detected for 3 sessions in a row.
There are also certain head lice shampoos and other products which contain a special type of insecticide (either natural or synthetic) which kills the lice. However, these are not 100% effective and some lice may be resistant to the active ingredients. Some of the approved shampoos may cause skin irritation and it is important to protect the eyes. The shampoo/product will need to be applied once initially, and then also 7 days later to kill any lice that have hatched after the first treatment. Not all insecticides are effective against the eggs. It is recommended that the hair is checked a few days after the treatment using the conditioner and comb method to ensure that the treatment has been successful. It is normal to find eggs after treatment and these should be brushed out. Finding an adult louse may mean that the treatment hasn’t worked (particularly if you find a considerable number) or more likely if there is only a small number, that there has been a re-infestation.
Luckily, head lice do not survive anywhere other than the hair on human head. Hence, unlike infections such as scabies (where the mite can live outside the body), it is not necessary to treat furniture, clothing or carpet. However, it is a good idea to wash the pillowcase on a warm cycle and to tumble dry it on a warm setting. It isn’t necessary to treat other members of the family for head lice if they are not affected, as the treatment will not prevent them from getting lice. Although it may be a little embarrassing, it is important to tell others who may have been in close contact with the affected person, so that they can be checked for lice and begin treatment to remove them. It isn’t necessary to keep your child home from school, as long as effective treatment has been started. Do make sure long hair is tied back to minimise the likelihood of spread to other children and it is also advisable to let the school know that there is head lice around.