Head Lice - Life Cycle, Descriptions & Symptoms

  • Added:
    Nov 03, 2012
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What are head lice?

The head louse, or Pediculus human capitis, is a parasitic insect that can be found on the head of human beings. Head lice feed on human blood several times a day and need to live close to the scalp to maintain their body temperature.

Head lice life cycle

The life cycle of the head louse has three stages: nit, nymph, and adult. The life cycle of a single louse from egg to mature adult capable of laying eggs or reproducing is about 21 days.

Nits/Eggs:

Head lice eggs are called nits. Nits are laid by the adult female louse and are attached to the base of the hair shaft by a strong cement like adhesive . They are located close to the scalp because they require body heat for incubation.

Size - 0.8mm by 0.3mm

Shape – Oval

Color – Yellow to white

Location – Within 6 mm of the scalp

Duration – Nits take 7 – 10 days to hatch.

Nymphs:

When an egg hatches, it releases a nymph. The nit shell stays attached to the hair and turns a dull yellow color. The nymph looks like an adult louse but is smaller. As the nymph grows, it molts out of its exoskeleton 3 times before it becomes an adult.

Size – Variable but about the size of a pinhead

Shape – Same shape as the adult louse

Color – Yellow to rust-colored

Location – Close to the scalp, especially behind the ears and at the neckline

Duration – Nymphs become adults after about 8-12 days

Adult:

The adult louse feeds about 5 times a day by piercing the skin with its claws, injecting irritating saliva, and sucking blood. Lice do not become engorged like ticks, but their color changes to a rust color after feeding. Head lice hold onto the hair with hook-like claws found at the end of each of their 6 legs. Adult lice are active and can travel quickly.

Size – The size of a pinhead. The female louse is larger than the male.

Shape – Oval with 6 legs and claws at the end of each leg

Color – Rust

Location – Close to the scalp, especially behind the ears and at the neckline

Duration – Adult lice can live up to 30 days on a person's head

Reproduction – An adult female can lay up 6-10 eggs a day.

How they spread

Head lice can be spread by direct contact with the head or hair of an infested person. The adult louse can survive for up to 1-2 days without feeding on the scalp; therefore lice can be found on objects that have been in contact with an infested person.

Why other lice treatments and shampoos don't work

RID and other lice shampoos only kill adult lice and adolescent nymphs. These shampoos work by attacking the bug's central nervous system. Because baby lice or "nyphms" have not yet developed a central nervous system, they cannot be killed by pesticides.

Lice Symptoms & Diagnosis

Common Symptoms of Lice

●              Scalp itching

●              Sensation of something moving in the hair

●              Red or pustular sores on the scalp caused by scratching

●              Swollen lymph nodes in the front and back of the neck

 

Detection and Diagnosis of Lice

Head lice and eggs are found almost exclusively on human head hair and the scalp, frequently around and behind the ears and near the neckline at the back of the head. Misdiagnosis of head lice is common.

The best way to confirm an active case of head lice is by finding a live nymph or adult louse on the scalp or hair. Adult and nymphal lice are very small, move quickly, and avoid light, so they may be difficult to find. Using a fine toothed louse comb helps in correctly diagnosing head lice.

 

What are head lice?

The head louse, or Pediculus human capitis, is a parasitic insect that can be found on the head of human beings. Head lice feed on human blood several times a day and need to live close to the scalp to maintain their body temperature.

Head lice life cycle

The life cycle of the head louse has three stages: nit, nymph, and adult. The life cycle of a single louse from egg to mature adult capable of laying eggs or reproducing is about 21 days.

Nits/Eggs:

Head lice eggs are called nits. Nits are laid by the adult female louse and are attached to the base of the hair shaft by a strong cement like adhesive . They are located close to the scalp because they require body heat for incubation.

Size - 0.8mm by 0.3mm

Shape – Oval

Color – Yellow to white

Location – Within 6 mm of the scalp

Duration – Nits take 7 – 10 days to hatch.

Nymphs:

When an egg hatches, it releases a nymph. The nit shell stays attached to the hair and turns a dull yellow color. The nymph looks like an adult louse but is smaller. As the nymph grows, it molts out of its exoskeleton 3 times before it becomes an adult.

Size – Variable but about the size of a pinhead

Shape – Same shape as the adult louse

Color – Yellow to rust-colored

Location – Close to the scalp, especially behind the ears and at the neckline

Duration – Nymphs become adults after about 8-12 days

Adult:

The adult louse feeds about 5 times a day by piercing the skin with its claws, injecting irritating saliva, and sucking blood. Lice do not become engorged like ticks, but their color changes to a rust color after feeding. Head lice hold onto the hair with hook-like claws found at the end of each of their 6 legs. Adult lice are active and can travel quickly.

Size – The size of a pinhead. The female louse is larger than the male.

Shape – Oval with 6 legs and claws at the end of each leg

Color – Rust

Location – Close to the scalp, especially behind the ears and at the neckline

Duration – Adult lice can live up to 30 days on a person's head

Reproduction – An adult female can lay up 6-10 eggs a day.

How they spread

Head lice can be spread by direct contact with the head or hair of an infested person. The adult louse can survive for up to 1-2 days without feeding on the scalp; therefore lice can be found on objects that have been in contact with an infested person.

Why other lice treatments and shampoos don't work

RID and other lice shampoos only kill adult lice and adolescent nymphs. These shampoos work by attacking the bug's central nervous system. Because baby lice or "nyphms" have not yet developed a central nervous system, they cannot be killed by pesticides.

Lice Symptoms & Diagnosis

Common Symptoms of Lice

●              Scalp itching

●              Sensation of something moving in the hair

●              Red or pustular sores on the scalp caused by scratching

●              Swollen lymph nodes in the front and back of the neck

 

Detection and Diagnosis of Lice

Head lice and eggs are found almost exclusively on human head hair and the scalp, frequently around and behind the ears and near the neckline at the back of the head. Misdiagnosis of head lice is common.

The best way to confirm an active case of head lice is by finding a live nymph or adult louse on the scalp or hair. Adult and nymphal lice are very small, move quickly, and avoid light, so they may be difficult to find. Using a fine toothed louse comb helps in correctly diagnosing head lice.

Author's Profile

. For anyone looking to treat head lice the safe way, the LouseBuster™ device uses only controlled, heated air, so it is very safe – even when used to treat people with asthma and those who have previously experienced side effects from other head lice treatment products. Please visit Pediatric Hair Solutions


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