Head lice are tiny wingless insects (2-3mm long) that live in the hair and feed on human blood. They vary in colour from cream to brown/black. They crawl quickly on the scalp and are difficult to see. They can only survive on humans.
What are nits
‘Nits’ is the common name for the small eggs that are laid by head lice. They are the size of a grain of salt, yellow-white in colour and are found firmly attached to the hair close to the scalp.
Common places for nits to be found are behind the ears, the back of the neck and the fringe. Dead nits are often black in colour and are found well away from the scalp.
Life cycle of head lice
Nits are laid on the hair shaft within 1cm of the scalp and take about 7-10 days to hatch into head lice. They will only hatch in a moist, warm environment such as the scalp.
If the lice are isolated from the head they die very quickly, generally within 24 hours, although in the NT's hot environment they can live longer than in other places in Australia.
How head lice spread
Anyone can catch head lice; regardless of cleanliness. Head lice are spread by direct hair to hair contact with another person who has head lice. Head lice cannot jump or fly from head to head but may be passed on by sharing hats and brushes. They are unlikely to be spread through bedding, furniture or carpets.
Head lice are commonly found in primary school-aged children because of their often close, personal contact with each other.
Head lice may cause itch and irritation, leading to sleep disturbance and behavioural problems. They do not transmit any infectious diseases.
Scratching resulting in skin breakage may lead to skin infections.
People with head lice may not always have symptom, therefore it is important to routinely inspect for head lice.
Silicone based occlusive products are the safest and most effective at killing head lice and are now the recommended head lice treatment in the NT.
The Hedrin® range contains 2 active ingredients; dimenticone (kills the adult lice) and nerolidol (kills the nits) and works by smothering the head lice. These products have no documented evidence of resistance and are able to be used repeatedly.
Treatments should be according to instructions on the packet.
- all household members should be checked for head lice and everyone with head lice should be treated at the same time
- apply first treatment to clean, dry hair (see wet combing technique below)
- a second treatment 7 days from the first treatment is recommended in case any nits have hatched.
If a child is found to have head lice, their school, play group, child care centre etc should be notified so other children can be checked and treated if necessary.
Previously, insecticidal products were the main treatment option. They kill lice chemically but unfortunately, these products have become less effective as lice have become resistant to them.
The active compounds found in insecticidal head lice treatments include:
- Permethrin – least toxic to people
- Pyrethrin – moderately toxic to people
- Malathion – most toxic to people.
Overuse of insecticidal head lice treatments does not assist in getting rid of head lice and increases the risks of side effects. Side effects may include mild irritation of the eyes, skin, nose and throat and if alcohol based products are used, pain or irritation of open sores and cuts.
Pregnant women, people with sensitive skin and parents of young babies should consult with a doctor before applying insecticidal head lice treatments.
Care should be taken to avoid having the product come in contact with the user’s eyes, nose or throat.
The person applying the insecticidal treatment product should wear protective gloves (to avoid unnecessary exposure to the treatment).
Manual removal of head lice
Wet combing with a silicone based occlusive product is recommended. Hair conditioner can be used but is less effective. You will need a general comb and a fine tooth head lice comb to manually remove the lice.
Conditioner does not kill lice but it immobilises them so that they can be combed out and manually removed.
Eggs may be removed by the combing process or can be picked off by hand but some may be missed. If using conditioner, this technique should be carried out every second day until no live head lice have been found for 10 consecutive days. For use of the occlusive silicone based agent, only 1 treatment is needed and another should be applied again in 7 days.
The wet combing technique:
- Apply occlusive product or conditioner to dry hair – use enough to cover the whole scalp and all hair from roots to tips.
- Use a normal comb to remove tangles and comb product evenly throughout the hair.
- Use a fine tooth/head lice comb to comb hair from scalp to tips.
- Wipe the comb onto a tissue after each stroke to remove immobilised lice.
- Comb all hair at least twice and leave product in hair for recommended timeframe (see product instructions).
- Thoroughly wash remaining product from hair.
‘Natural’ and other products
There are no formal controlled clinical trials to demonstrate the effectiveness or side effects of tea-tree oil, eucalyptus or kerosene for treatment of head lice.
If treatment does not work
True treatment failure has occurred when live lice are found immediately after treatment.
Treatment failures may result from:
- inappropriate treatment technique
- hatching of lice from eggs since the last treatment
- resistance of head lice to a particular treatment product
- re-infestation from others who have been inadequately or not treated
- eggs found more than 1cm from the scalp do not represent treatment failure, they are usually dead or hatched eggs. Dead nits are dark/black in colour.
- change to a different category of treatment product. If you have used an insecticidal product, change to an occlusive product
- increase fine combing (eg twice daily)
- seek advice from a doctor or pharmacist.
Prevention of head lice
There are no products available to prevent head lice.
When lice are present in the community, simple strategies for prevention include:
- weekly hair and scalp checks
- wet combing frequently with nit combs
- avoid sharing brushes, combs, hats, pillows
- washing brushes and combs once a week in hot soapy water
- keeping long hair braided or tied back.
It is recommended that all children have their hair and scalp checked for head lice 1 week prior to returning to school. Effective monitoring and treatment during school holidays reduces the spread of head lice throughout the community.
For more information contact the Centre for Disease Control.
Last updated: 20 March 2020
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