Head lice (Pediculus humanus capitis) are one of the many varieties of sucking lice (singular "louse") specialized to live on different areas of various animals.

As the name implies, head lice are specialized to live among the hair present on the human head and are exquisitely adapted to living mainly on the scalp and neck hairs of their human host. Lice present on other body parts covered by hair are not head lice but are either Pubic lice (Pthirus pubis) or Body lice (Pediculus humanus humanus).

Description
The adult head louse resembles a miniature ant that appears flat when viewed from the side through a strong magnifying glass. Head lice have a head, thorax and abdomen with six legs, but their two front legs are very large in order to grab onto the hair shafts. Head lice are tan to greyish-white in color.

Life cycle
Lice eggs on the hair very close to the scalp are the primary sign of an active infestation. The female louse glues her eggs, sometimes called "nits", which look like tiny white beads, to hair shafts very close to the scalp. Eggs are very small, about the size of a period (full stop) in normal printing. Eggs may appear yellowish, brownish or greyish, but almost always lighter colored. Eggs normally undergo a 7-9 day incubation before hatching as a baby nymph. Classically, a louse egg does not become a "nit" until after it has completed its incubation stage, thus leaving a "nit". A "nit" is either the empty shell remaining after the nymph has departed or the dead egg that remains if incubation was not successful. Dead eggs will appear dark, or raisin-like, as they dry out. "Nits" are usually found one-half inch or more away from the scalp and are not considered a sign of an active infestation.

There are three nymph instar stages as the baby louse matures, with the louse shedding its exoskeleton at the end of each stage as it gets larger. The nymph stage typically lasts 10 to 12 days.

Whether a louse is male or female is not apparent until they are nearly mature. Fertilization of eggs takes place once the female reaches the mature stage. The female can then lay 3-7 eggs each day for the next 28 to 30 days, her normal life span.

There are three main stages in the life of a head louse: the nit, the nymph, and the adult.

Nit: Nits are head lice eggs. They are hard to see and are found firmly attached to the hair shaft. They are oval and usually yellow to white. Nits take about 1 week to hatch.
Nymph: The nit hatches into a baby louse called a nymph. It looks like an adult head louse, but is smaller. Nymphs mature into adults about 7 days after hatching. To live, the nymph must feed on blood. It metamorphoses 3 times before it reaches the adult stage.
Adult. Females lay nits (a few hundreds of eggs); they are usually larger than males. To live, adult lice need to feed on blood. If the louse falls off a person, it dies within 1-2 days.
 

Symptoms
The louse feeds on human blood, and the bite causes itching. Bites can become secondarily infected; scratching may break the skin and help cause this secondary infection. The most common symptom is itching of the scalp.

Head lice are normally spread by close contact but can also be spread by sharing clothes.

Treatment
The most common Western treatment is with chemical insecticides such as pyrethrin; however, there is increasing controversy over possible toxic side effects. For more information as well as alternate treatments,
The source of this article is Wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL
 

Web www.best-discount-gifts.com

Real Ways to Get Rich on the Internet!

Medical Resources:

Post nasal drip, lose weight, diabetes, Alzheimer's, more

Guides for Better Living

How to Cope with Life's Problems

Household Tips:

how to clean athletic shoes, get rid of roaches

Help for Senior Citizens:

Avoid scams, more...

*This site does not provide medical advice.
The contents of this site, such as text, graphics, images, information and other material ("Content") contained on the this site, is for information purposes only. The Content is not intended to be a substitute for professional medical advice, diagnosis or treatment (and the Site does not render medical, nursing, or professional health-care advice in any jurisdiction). Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or medical treatment. Never disregard professional medical advice or delay in seeking it because of something you have read on this Site.

If you think you may have a medical emergency, call your doctor, or 911 or other emergency service number immediately. Our site does not recommend or endorse any specific tests, products, procedures, opinions or other information that may be mentioned on the Site. Reliance on any information provided by this Site is solely at your own risk.