Pediculosis humanus Capitis is an obligate human parasite.
- Spread is mainly through head to head contact – lice can move from one head to another in seconds
- Spread via fomites is probably low
- Pruitus occurs in response to mite saliva, but may take several weeks to develop
- Recurrent infection may result in skin desensitisation and little itch
- Pruritus results in scratching, with secondary folliculitis and impetigo
- Eggs (nits) are visible firmly attached to hair shaft, usually within 1cm of scalp and require manual removal
Life Cycle of Head Lice:
- Insecticides: none can guarantee to kill all eggs – those not killed or removed manually will hatch 7-10 days after being laid.
- An important part of management therefore involves manual removal of eggs with a ‘nit comb’ after treatment with an insecticide.
- Metal ‘nit combs’ are probably superior, however, children with coarse hair may require a plastic comb with slightly wider spaces between the teeth.
- The addition of hair conditioner prior to combing may ease the process.
- Risk of transmission via fomites is probably low but washing bed linen in hot wash and sun drying is recommended.
- Close contacts should be checked for evidence of infestation, and treated at the same time.
- Resistance to pyrethrins has been reported internationally, therefore it is appropriate to use a different type of insecticide if the infestation is not adequately treated or recurs.
- Permethrin 1% rinse/shampoo (e.g. Pyrifoam)
- Used in infants over 6 months
- Apply to towel dried hair, leave for 10 minutes, and then nit comb out hair
- Repeat seven days later
- Dimethicone 4% lotion: ‘Hedrin’: method of physical control
- Available over the counter
- Applied to entire length of dry hair, left 8 hours or overnight. Combed out with nit comb.
- Repeat in 7 days
The 10 Day Conditioner Method:
- The saturation of dry hair with hair conditioner (any type) will immobilise fast moving lice, allowing manual removal with a nit comb
- The procedure must be repeated daily for 10 days to ensure removal of new lice as they hatch
- Examine combings on white paper
- The presence of dark adult lice (hatchlings are paler) after day 1 means that the process must be restarted as this represents a new infestation and new eggs are likely to have been laid
- Concentrate on removal of eggs closest to scalp as those >1cm from scalp are likely to already be hatched or dead
- Check for reinfestation after 4 weeks
- A magnifying glass and using white coloured conditioner make lice easier to see
Other: e.g. tea tree oil, sassafras oil – there is no evidence that other products are effective.
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