The life of a louse


The head louse is a blood-sucking insect that has a three stage life cycle: egg, nymph, and adult.


Eggs: Nits (head lice eggs) are small, silvery-white, oval-shaped eggs that are attached to the hair shaft very close to the scalp. They are hard to see and are often confused for dandruff or shampoo/hair product residue that will not wash off. Nits are laid by live lice - you cannot ‘catch’ nits. Once laid, nits take about



1 week to hatch (6 to 9 days).


Nymph: Once hatched, the nymph (baby louse) is clear-coloured, about the size of a pinhead, and must feed within 45 minutes to survive. After feeding they develop a reddish-brown colour. The nit shell remains attached to the hair shaft, but if found more than 6mm from the scalp, it has already hatched. Nymphs


mature and begin breeding 7-10 days after hatching.


Adults: The adult louse is about the size of a sesame seed, has 6 legs each with claws to grasp the hair, and is tan to greyish-white


in colour. Female lice may lay up to 8 nits a day, and can live up to a month on a host.


Symptoms of head lice


The primary symptom of head lice is itching (and subsequent scratching) caused by the lice feeding on blood. As they eat, they inject their saliva into the wound. The saliva contains a chemical that prevents the blood from coagulating,


and also causes irritation and subsequent allergies in the human host scalp.


Examination of the hair and scalp will reveal white or grayish crawling lice forms and yellowish white eggs attached to the hair


shafts close to the scalp. Sometimes the


eggs are mistaken for dandruff that will not wash


off. Occasionally red bite marks or scratch marks can be seen on the back of the neck or behind the ears.


Treatment for head lice


Most head lice treatment products are quite effective at killing the live lice – but the eggs are a different case. No treatment kills 100% of the eggs, as the shell is quite difficult to penetrate, so retreatment is always necessary.





The most effective treatment regimes involve three treatments, each 7 days apart. By re-treating after 7 days, you ensure that any newly-hatched nymphs are killed before they begin to lay eggs. The third treatment at 14 days will kill off any lice


that are late in hatching. By killing nymphs before they grow to adulthood, you can break the life cycle of the louse.


It is also important to remove the lice after each treatment with a fine tooth nit comb – being thorough at this can greatly


increase your chances at success!


To kill any live head lice on exposed clothing, bedding, hairbrushes and toys, you can soak the items in hot water (>53.5°C) for 5 minutes, or seal them in a plastic


bag and store them for two weeks. Lice cannot survive this length of time without a food source.


The other key to successful eradication of head lice is to inform the parents of your child’s friends and playmates that you are treating head lice. If you can treat at the same time, you are more likely to get rid of the lice for good.


Ask the friendly staff at your local DCO pharmacy for advice on the best head lice treatment for your family.


The Facts


  • Head lice infestation is not related to cleanliness of a person or their environment.
  • Head lice do not hop, jump or fly – they are a crawling insect - and must have very close head-to-head contact to spread.
  • Head lice are a human parasite only – so you can’t blame the dog!


  • Adult head lice need to feed on human blood at least every six hours, and will die within 24 hours of leaving their human host.
  • Head lice are not known to transmit any disease and therefore are not considered a health hazard – they are just a nuisance!


DISCLAIMER: This material contains general information about medical conditions and treatments and is intended for educational purposes only. It does not constitute medical or professional advice, nor should it be used for the purposes of diagnosing or treating any illness. If you have or suspect you may have a health problem, you should consult your local pharmacist or health care provider to obtain professional advice relevant to your specific circumstances.