About Head Lice & Nits
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Head lice (Pediculus humanus capitis) are tiny wingless insects about two millimetres long which live on the scalp and neck of humans. When an infestation occurs there may be up to 12 adult lice on the scalp at any one time. They feed from human blood and must eat at least twice a day; they cannot survive for more than one day at room temperature off a human body. A female louse can lay eggs at the rate of about six per night up to a total of 100.
Enlarged Pictures of head lice
Female lice that are approximately 7 days old have generally reached reproductive maturity. At this point in their life they lay seven to 10 takes a day. The eggs are usually called nits. The eggs/nits are a white-translucence color and are very close to the scalp. The nits require a fairly constant temperature range so they are placed within 1 inch of the scalp preferably in a congested area of hair.
When the adult female louse lays the egg on the hair shaft she uses a glue like substance to attach it. As the hair grows, so the nits (or their empty shells) are carried away from the scalp and are more easily visible. Nits can often be mistaken for dandruff, flakes of dry skin or other small items caught in the hair.
Enlarged Pictures of nits or eggs
What causes head lice and who is at risk?
Head lice cannot fly and they cannot jump from one person to the next; they are not transmitted from household pets or other animals. Instead, when they are caught, it is usually through head-to-head contact or by sharing hair accessories, such as hair-brushes, combs, hats or even by putting these items on top of each other. Head lice can also survive for short times on bedding and furniture.
Children are particularly prone to infestation with head lice as they often have close contact with each other at school or when playing. There is no link between the presence of head lice and a lack of hygiene or susceptibility to infection.
What are the common symptoms of head lice?
Often the first sign of infestation is an itchy head or neck. The saliva of head lice is irritating on the skin, and itching is often worse behind the ears or at the back of the neck. However, head lice do not always cause itching. In some developing countries, human head lice have been blamed for passing rare diseases from person to person.
In the United States and other devolped nations, lice do not usually cause direct harm to an affected person but the persistent irritation and itching can disturb concentration and disrupt sleep. When trying to eradicate the lice, care should be taken not to overuse potentially hazardous medicines.
How do I recognize head lice?
The only way of confirming an infection with head lice is by seeing either the adult lice or their eggs in the
hair. The lice tend to stay close to the scalp and move away from direct light, but the nits are stuck to the
hair shafts. In searching for nits and/or lice, the following are important:
- clean, tangle-free hair,
- bright light, especially natural light,
- use of a fine comb and start combing at the roots of the hair,
- using a magnifying glass may be helpful.
Nits may be distinguished from, for example, dandruff, by trying to move them off the hair shaft. As they have been firmly attached by the parent lice, nits are not easily removed. Even after treatment, empty nit shells may remain stuck to the hair. The shells tend to look whiter and more shiny, and to be more than 0 to 1 inch away from the scalp. They are not a sign of re-infestation.
Where are the lice and nits?
Head lice generally like a dark, warm place. They tend to congregate behind the ears or above the nape of the neck. Since they gather there, they tend to lay their eggs there. If you have a child that wears ponytails or any hair that is clumped together, look at the base of that area. Lice do not always stay in those areas but they are most commonly found there. See the graphic below for ideas on where lice and nits may most likely be found.
Head lice and nit life cycle
The life cycle of the head louse is a short one. They usually live only about 17 days total from the time they hatch. When a newly hatched louse emerges, there is about a 7 day period until they reach reproductive maturity. Then they lay around 10 eggs a day for around 10 days. During this time they "chew" into the scalp for blood. They use only human blood to digest food. Head lice have specific enzymes that digest only human blood. They can not live on any other animal.
Since lice "chew" into the scalp for blood, they leave 100's of tiny scabs on the scalp. This is the usual cause of itching.
10 adult female lice lay approximately 100 eggs per day on the hair shafts. You can realize how nit-picking is so tenuous because if you just miss a couple, the reinfestation takes place all over again.
The problem with nit picking
Nit picking is the most common misguided form of control for head lice among medical and school professionals. It does not work. If it did, there would be no lice left
Here is the usual scenario: Head lice are discovered after itching. You run to the pharmacy and buy the pesticide based Rid or Nix. You apply it but it doesn't kill all the live lice.* The instructions say to wait 9 days before re-application but you are desperate and get another box to put on. Finally, you think you have killed all the live lice but now you have to get the nits. You pick through the possible thousands of nits. The nurse examines the head and agrees that there are no more nits. However, 2 (or more) nits were missed by both people. Those nits take 14-20 days to hatch. The new hatchlings start eating at the scalp but since there are only a couple of them, they go unnoticed. 7 days later those hatchlings are now reproductive adults and start laying 10 eggs a day. In 14-20 days they all hatch and soon the itching begins. Many people (including the school medical professionals) think that the child has be RE-infested when actually, a couple of nits were originally missed. This is why nit-picking is ineffective.
The National Association of School Nurses and The American Academy of Pediatrics both agree that nit-picking is NOT the answer. Too many children are left home due to no-nit policies. Nit are not the ones that are transmittable anyway, it is the live lice that move.
The National Pediculosis Association SUPPORTS the no nit policy vehemently. However, even though the NPA is a nonprofit organization their administrators get a paycheck from the Association. And one of the main ways they make their money is by selling a lice comb (the LiceMeister comb http://www.headlice.org/licemeister/index.htm). I find this to be an incredible conflict of interest and am disgusted by their practices. They operate under the guise of helping children with head lice but actually they are probably con-artists getting government grant money while selling products for profit.
The American Academy of Pediatrics ( http://aapnews.aappublications.org/cgi/content/citation/21/3/113) and the National Association of School Nurses ( http://www.nasn.org/Default.aspx?tabid=237) are both AGAINST "no nit" policies.
* Rid and Nix are both pesticide based head lice treatments. The Food and Drug Adminstration (FDA) puts a limit on how much pesticide can be put on a human being with minimal safety liabilities. The FDA puts a cap on how much pesticide can safely be put on a human. Rid and Nix (and any other pesticide based product) have a problem because head lice have become immune to the capped amount of pesticide that is considered safe. Head lice are now immune to the levels of pesticides delivered by Rid and Nix. The FDA orders Rid and Nix to put a disclaimer and orders them to put a 9 day wait period before reapplication of the pesticide. This does not hinder desperate caregivers though to ignore the warnings. When the one dose of pesticide based head lice treatment does not work, the caregiver usually goes and buys (and applies) more highly unsafe and dangerous pesticide levels on (usually) a small child. DO NOT USE PESTICIDE BASED HEAD LICE TREATMENTS!
Head Lice and nit cycle (visual)
Reproductively mature females lay 8-10 eggs a day!
Eggs/Nits are glued to the hairshaft.
The Nit/Egg take 14-20 days to incubate in a warm place near the scalp before hatching.
A newly hatched nymph needs to find a human bloodmeal quickly
A nymph will reach reproductive maturity in about 7 days from hatching.
At around day 7 the mature adults will reproduce and create about 10 eggs a day.