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Head lice are the bane of many parents' lives. Why are they so hard to get rid of? Why can't you drown them? Why does it take so much combing?
Male headlouse on a human head Photo: [http://en.wikipedia.org/wiki/Head_louse#/media/File:Male_human_head_louse.jpg]
They have been found on the heads of Mummies from 2000 BC, and their anatomical structure has not changed since.
Head lice live on human blood, have six legs and can hold on to hair shafts, where they literally glue their eggs, or nits, close to the scalp.
That is partly why they are so hard to get rid of. Even if you can capture the live lice, which can speed around the scalp, the tiny nits are so well glued to the hair shaft they often escape unscathed. Even pesticide treatments do not penetrate the egg.
Professor Rick Speare, public health physician and expert on head lice, answers some questions about lice and busts a few myths.
Many lice treatments are pesticide based. Are lice becoming resistant to the pesticides?
Yes, but there are some new products on the market now which are changing the picture. Their active ingredient is Dimethicone, a long chain of silicone atoms. This gets into the breathing structure of lice and blocks their breathing holes, or stops them losing water, which makes their intestines explode.
Why can't you drown them by taking a long bath or going for a swim?
Lice have evolved with humans, and we have always put our heads in water. They are designed to resist it. The louse shuts itself down, it is called sham death, and when you take it out of the water it recovers within five minutes.
How essential is a nit comb for getting rid of head lice and nits?
With some of the new Dimethicone based products, some of the silicone based oils penetrate the egg too, so the embryos die as well. In that case you don't have to comb them all.
But most strategies involve combing since most insecticides don't penetrate the egg.
If using a nit comb by itself the lice just run away. You need to immobilise them first with conditioner (more on this below).
Some claim that brushing and combing hair regularly breaks the legs of the lice, stopping them from being able to move and reproduce.
No it won't. This is not true. A study involving two school classrooms in Victoria tested this theory. The higher rate of lice at the end of the study was in the class that combed their hair vigorously compared to the class that did not. This is because combing creates an electric charge on the hair and the lice, which can repel the lice from the hair across to other students making it easier for them to spread to nearby heads.
Is dying your hair a good way to get rid of lice, or prevent them?
No, it is a good way to hide eggs. If you dye your hair black, the hair dye will make the eggs disappear as they will become the same colour as the hair. The kids that get sent home for head lice are often the ones with black hair and dead eggs, which are white and therefore stand out more easily.
Is it true they don't like hairdryers?
Yes this is true. It is hard to kill them with hairdryers however.
Photo: AFP / CHASSENET / BSIP
If a child in the family has head lice, do you really have to wash their bedding in hot water?
No, it's a waste of time. Once off the head they are in strife.
We did a study with over 2000 schoolchildren, counting lice on heads and looking for lice on school carpets. 14,033 lice were found on the pupils heads and none on the carpets. Then we looked at heads of children with lice and the children's pillowslips. Only a small percentage of lice were found on the pillows and most were dead.
They die within 12 hours of being off the human head. Putting the pillowcase in the clothes dryer on hot for a five minutes is enough to kill lice.
Do natural home remedies like vinegar and olive oil work?
Some believe vinegar loosens the eggs from the hair shaft. This is not true. In the past people have used kerosene, but this is very dangerous as it is so flammable.
There is no scientific research that I know of on olive oil, but coconut oil does have a natural repellent though we are not sure if it kills the lice.
Natural lice treatments often have a number of active ingredients which stun the lice so they stop moving, but may not die. But hair conditioner has the same impact.
Professor Rick Speare talks about head lice with Kathryn Ryan on Nine to Noon.