Signs and Symptoms of Head Lice

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Head lice (Pediculus humanus capitis) are parasites that live in your hair and feed off the blood from your scalp. Although head lice are harmless and don’t spread disease, they can cause a great deal of discomfort and distress.

Transmitted by close contact and known to spread quickly, head lice are most common among children ages 3 to 11. In fact, up to 12 million head lice infestations occur each year in the United States within that age group alone. To keep your family head-lice-free, learn how to spot the signs and symptoms of infection such as itchiness, discolored bumps, and visual cues.

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Frequent Symptoms

Lice move very quickly so they’re not always easy to see. To detect a head lice infestation look out for the following symptoms:

  • extreme itchiness in your scalp
  • a tickling or crawling sensation on your head
  • small red bumps on your scalp or neck

If you think your child may have head lice, watch for the following signs:

  • frequent head-scratching
  • sores on the head (the result of frequent scratching)
  • small red bumps on the scalp or neck

Because lice are particularly active in the dark, they may also disrupt your child’s sleep. Therefore, difficulty sleeping and daytime irritability may be a sign.

Head lice are highly contagious, especially when sharing hairbrushes, hats, and other personal belongings. Therefore, it’s a good idea to check everyone in your family (and other close contacts) if someone in your household is found to have them.

Visual Signs

About half of people with head lice will not scratch their head, so the best way to detect an infestation is to look for signs of an infestation. By parting the hair and examining the scalp in bright light (ideally with a magnifying glass and fine-tooth lice comb), you may be able to get a close look at head lice. The insects are generally easier to see near the ears and the nape of the neck.

Head lice are wingless and have three forms: the egg (or “nit”), the nymph, and the adult. Here’s how to spot each form.

Nits

Oval-shaped and extremely small (i.e., just about the size of a knot in thread), nits are frequently found on the back of your neck or behind your ears. Since they often appear white in color, they’re sometimes mistaken for dandruff. Unlike dandruff, however, nits are attached to individual hairs (often close to the scalp) and won’t fall out when the hair is shaken.

Nymphs 

A type of louse that’s recently hatched from the nit, a nymph resembles an adult louse (often grayish-white to tan in color) but is smaller in size. It takes nine to 12 days after hatching from the nit for a nymph to mature into an adult.

Adult Lice

Adult head lice are about the size of a sesame seed. They have six legs, featuring hook-like claws that allow them to cling tightly to the hair shaft. Often grayish-brown or tan in color, adult head lice may appear darker in people with dark hair than in people with light hair.

Note that while head lice are found almost exclusively on the scalp, it’s possible (though very rare) to find lice on the eyebrows or eyelashes as well.

Complications

Along with emotional distress and sleep disturbance, head lice can lead to a number of complications when left untreated. For example, frequent scratching can cause breakage of the skin, which can leave you vulnerable to infection.

Since lice feed on human blood, severe chronic infestations can lead to blood loss and iron deficiency anemia. In addition, an allergic reaction to louse feces or bites may trigger a rash in some individuals.

Know that in most cases these complications are rare. Lice are generally harmless, but they are important to get rid of.

Frequently Asked Questions

How long after exposure do lice symptoms appear?

Nits take anywhere from 8 to 9 days to hatch into nymphs. Thereafter, it takes nymphs 9 to 12 days to mature into adults. Adults can live for around 30 days if they have access to blood.

People can start having symptoms when nits begin to hatch into nymphs. The intensity of symptoms can intensify as adults start laying eggs and the lice population grows rapidly in size

What are the symptoms of lice?

Head lice infestations often cause intense itchiness and a tickling sensation around the base of the hair. Sores can develop from scratching, some of which may become infected. Many people have difficulty sleeping as lice are more active at night. Irritability is also common.

Some people with head lice may experience no symptoms for weeks and only find out they are infested when a schoolmate or family member is diagnosed. Even so, they are still able to spread lice.

What are the symptoms of body lice?

The symptoms of body lice (Pediculus humanus corporis) are similar to those of head lice. The lice are mainly found in infested bedding and clothing and occasionally on body hair.

In addition to intense itchiness, body lice can cause rash, bumps, and a darkening of the skin around the waist or in the groin (where lice often flourish if left untreated). 

There are also pubic lice (Pteris pubis) that reside mainly in pubic hair and are more commonly known as "crabs."

What do head lice look like?

The adult louse is roughly the size of a sesame seed with six legs tipped with tiny claws. The body of the insect may be beige or grayish-white in color. Nits look similar to an adult louse but are far smaller and more difficult to see.

People with head lice will often be able to see the eggs attached to the base of hair shafts, which can look like minuscule whitish flecks or droplets.

A Word From Verywell

It’s important to seek medical attention if you suspect that anyone in your family has head lice. You should also talk to your doctor if you or your child is still experiencing head lice symptoms even after using an over-the-counter treatment. In some cases, a stronger product may be needed in order to eliminate the lice.

Head Lice Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

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Article Sources
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  5. Althomali SA, Alzubaidi LM, Alkhaldi DM. Severe iron deficiency anaemia associated with heavy lice infestation in a young womanBMJ Case Rep. 2015;2015:bcr2015212207. doi:10.1136/bcr-2015-212207

  6. Centers for Disease Control and Prevention. Head lice; frequently asked questions (FAQs). Updated September 7, 2020.

  7. Cummings Carl, Finlay JC, MacDonald NE. Head lice infestations: A clinical update. Paediatr Child Health. 2018 Feb;23(1):e18-24. doi:10.1093/pch/pxx165

  8. Centers for Disease Control and Prevention. Body lice: frequently asked questions (FAQs). Updated August 31, 2020.

  9. Centers for Disease Control and Prevention. Public lice: frequently asked questions (FAQs). Updated September 17, 2020.

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