Advice on treating head lice.
Only the presence of a live adult louse can prove you have head lice. Dried husks of eggs or skin moults of nymphs can only prove you have had contact or been in the same place as another person who has head lice. So no live lice means no infection.
Treating head lice
Firstly NO treatment works 100% on just one application, most will need to be repeated. There is resistance to all the chemical treatments, and this will vary with country and area within countries. So my advice is if you want to go down the chemical road buy two different types and use one one week and another the week after. The electric lice combs tend to clog up and stop working. For more details see below left.
A recent study by the London School for Hygiene and Tropical Medicine found that the old-fashioned hand combing method worked better than all the others, but it must be repeated. To make the combing easier you can apply conditioner or even olive oil, then rinse it out. You'll end up with lice-free, well-conditioned, glossy hair. Do this every 5 - 7 days until you can find no lice, then you are lice free. If outbreaks are common then it might be a good idea to do this regularly as a check.
Active ingredient in some chemical treatments
Malathion containing treatments. These are applied to dry hair and left on for at least eight hours. The treatment may cause stinging when the alcohol enters wounds made by scratching and lice.
Lindane containing treatments. Lindane is a neurotoxin, so be very, very careful and follow the instructions. It should be kept on wet hair for just four minutes.
Permethrin containing treatments. These should be left on the hair for just 10 minutes.
Pyrethrin containing treatments. These are usually applied as a shampoo to wet hair and left in for 10 minutes.
Some of the above treatments are unsuitable for pregnant women and babies, so do read the instructions very carefully.
Other non-insecticide shampoos are much safer, but will have limited use, so you will end up with cleaner lice.
- Some things to remember.
A louse away from human hair will die within 55 hours
- Eggs take 7 - 10 days to hatch
- So one treatment/combing may get most of the adult lice, but to keep lice free you have to make sure there are no adult females to lay eggs and to get all the hatched lice from the eggs already there
- The most common areas to find lice are behind the ears and at the back of the neck
- A louse needs a blood meal every 3 - 6 hours
Crab louse Phthirus pubis
Above is the crab louse Phthirus pubis. It has recently been discovered that the Crab louse is most closely related to the louse that lives on gorillas! Apparently they were one species around 3.3 million years ago.
The eggs are slightly smaller that the head and body louse eggs, and are glued firmly to the body hair. Eggs hatch in 7 - 8 days. There are 3 nymphal stages. The nymphs become adult in 13 - 17 days. It takes several hours for the insect to drink its blood meal. The adult dies if removed from the host for more than 24. It is found on pubic hair, eyelashes and eyebrows. Transmission is through sexual contact usually, but can occur via infested clothes or towels. It does not transmit disease, but the saliva of the louse causes skin irritation.
Body louse or clothing louse
Originally the body louse and head louse were a single species. The lifecycle is similar to that of the head louse, except that the eggs are glued to clothing - usually around seams - as well as body hair. The body louse female can lay over 100 eggs in her lifetime. Feeding usually occurs while the host is asleep. At other times the louse rests in the clothing. Body lice can withstand longer periods of starvation that head lice. Transmission is usually through infested clothing or bedding.
Louse bites are irritating and infection can enter wounds caused by scratching the bites. Where there are good hygiene facilities available lice are easily treated, and in healthy humans should cause no real health problems, though with schoolchildren outbreaks do seem to be occurring more frequently. Where hygiene facilities are poor, lice infestations can become debilitating through lack of sleep, and dangerous through transmission of diseases and wound infection. The body lose can carry the bacteria that cause typhus, trench fever and relapsing fever.