What are head lice?

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

What does head lice look like?

Head lice have a life cycle with three stages

Egg/Nits: These are lice eggs laid by the adult female louse at the base of the hair shaft near the scalp. The eggs are firmly attached to the hair shaft and are oval-shaped and very small and hard to see. Eggs vary in color from clear to light brown to yellowish-white. They are often confused with dandruff, scabs, or hair spray droplets. Eggs are usually located no more than 1/4in (.635cm) from the base of the hair shaft. Eggs usually take about 8-9 days to hatch.

Nymphs: A nymph is the immature louse that has recently hatched from the egg. Nymphs look like adult lice, but are smaller.  Like adult lice, nymphs must feed regularly on human blood.
Nymphs mature into adults about 9-12 days after hatching from the egg.

Adults: The fully grown adult louse is about the size of a sesame seed, has six legs, and is tan to grayish-white in color. To survive, adult lice must feed on blood. An adult head louse can live about 30 days on a person’s head, but will die within 24-48 hours if it falls off a person.

What are the symptoms of head lice?

  • An itchy scalp
  • A tickling feeling of something moving on the scalp or through the hair
  • Red bite marks on the scalp caused by excessive scratching or a red rash on the back of neck

How They Spread

These critters move from head to head, hat to head, pillow to head, comb to head…If it’s been on someone’s  lice ridden noggin, it could very well be a source of infestation.

Detection & 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. Head lice and eggs are sometimes also found on the eyelashes or eyebrows, but this is uncommon. Misdiagnosis of head lice is common.

The best diagnosis is by finding a live nymph or adult louse on the scalp or hair of a person. 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.