Head Lice Infestation: Causes, Symptoms & Diagnosis
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Head Lice Infestation

What Are Head Lice?

Head lice are small, wingless, blood-sucking insects. They live in the hair on your head and feed off the blood from your scalp. A louse (a single adult) is about the size of a sesame seed. A nit (louse egg) is about the size of a small flake of dandruff.

Find treatments to get rid of lice using Healthline's Buyer's Guide »

What Causes Head Lice?

Causes

Head lice are contagious. You can become infected with head lice when the insects crawl onto your head. Ways you might get head lice include:

  • touching your head to an infected person’s head
  • sharing the personal items (e.g., comb) of someone with head lice
  • using a fabric item after an infected person

Lice can be transferred by brushes, combs, barrettes, headbands, headphones, and hats. They can also live for a time on upholstered furniture, bedding, towels, or clothing.

Who Is at Risk for Head Lice?

Risk Factors

Preschool and elementary school students have the highest risk of getting head lice. They tend to play closely together and share items that touch their heads. There is also an increased risk of head lice for family members of school-aged children. People who work in a day care center, preschool, or elementary school share this risk.

What Are the Symptoms of Head Lice?

Symptoms

Symptoms of head lice include:

  • extreme scalp itchiness
  • feeling like something is crawling on your scalp
  • sores and scabs on your scalp from scratching

How Is Head Lice Diagnosed?

Diagnosis

You or your healthcare provider can diagnose head lice by:

  • checking your hair, close to the scalp, for lice
  • checking your hair, close to the scalp, for nits
  • running a fine-toothed lice comb through your hair, starting from the scalp, to catch lice and nits

The nits are dark-colored and hatched lice will be light-colored.

Adult lice move quickly. You will most likely find nits if you find any evidence of head lice on your scalp.

You can easily differentiate between nits and dandruff flakes or other debris in your hair. Most debris should be removed easily. Nits will seem like they are cemented to your hair.

Head lice are contagious. If one person in your household has them, others may too. It’s a good idea to check everyone (in the household) for signs of lice every few days.

How Are Head Lice Treated?

Treatment

There are several head lice treatments available. Most treatments will need to be used twice. The second treatment, after a week to nine days, will kill any newly hatched nits.

Some of the major treatments for head lice are described below.

Medications

There are both over-the-counter (OTC) and prescription head lice treatments.

Two types of chemicals are commonly used in OTC head lice treatment.

Pyrethrin is a pesticide that is derived from chrysanthemum flowers. It is approved for use in people 2 years old and older. Do not use pyrethrin if you are allergic to chrysanthemums or ragweed.

Permethrin (Nix) is a synthetic pesticide that is similar to pyrethrin. It is approved for use in people 2 months old and older.

Prescription lice treatments may also include other chemicals.

Benzyl alcohol lotion (Ulesfia) is an aromatic alcohol. It is used to treat head lice in people 6 months old and older.

Malathion (Ovide) is an organophosphate pesticide. It is used to treat lice in people who are 6 years old or older. It is not recommended for women who are pregnant or breast-feeding. Malathion is flammable. Stay away from open flames and heat sources such as hair dryers when using this product.

Lindane is an organochloride pesticide. It is available in lotion or shampoo forms. Lindane is usually only used as a last resort. It can cause serious side effects, including seizures and death. Lindane should not be used by premature babies or by people who have a history of seizures.

In order to reduce the risk of side effects:

  • Do not use more than one medication.
  • Do not use any medication more often than directed.

Alternative Treatment

If you want to avoid using pesticides, use a fine-toothed lice comb or a flea comb (sold in pet stores) to remove lice. Apply olive oil to your hair before combing. This will help the lice and nits stick to the comb. Start combing at the scalp and work through the end of the hair.

You will need to do this every two to three days until you have no more signs of lice or nits.

Treating Your Home

There is no need to use pesticides around your home. Lice cannot survive more than a couple of days off your head. The following methods can be used to kill lice on different items:

  • wash clothes and bedding in hot water (130 degrees Fahrenheit or above) and dry on high heat in the dryer
  • dry-clean clothes and bedding
  • seal clothes, bedding, and plush toys in a plastic bag for two weeks
  • soak hair brushes, combs, barrettes, and other hair accessories in hot water (130 degrees Fahrenheit) for five to 10 minutes
  • vacuum floors and upholstered furniture

Long-Term Outlook

Outlook

You can get rid of head lice with the proper treatment. However, you may become reinfected. Reduce that risk by cleaning your house properly and avoiding contact with other infected people until they have been treated.

You can reduce your chances of getting head lice by not sharing personal hygienic items with others.

How Do You Get Head Lice? »

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Lice Emergency? A Parent’s Guide to Lice Outbreaks
Lice Symptoms
Body Lice Infestation
Scalp Scabs: Causes and How to Treat Them
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