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Head Lice


Head lice are tiny parasites that feed on blood as a source of their food. They are very small in size, almost equivalent to the size of a sesame seed. These insects lay eggs on your scalp and grow in population. Contrary to popular belief, head lice do not result from poor hygiene or lack of cleanliness. They are contagious and can spread from one person to another by direct or indirect contact. There are multiple treatment options available for head lice. The efficacy of each treatment option may vary for different individuals. 


Head louse or Pediculus humanus capitis is an ectopic parasite that feeds on blood. This louse lacks wings, so it cannot fly from person to person. The common mode of transference of head lice is direct head-to-head contact. This is common among school-going children who often play in small, close groups. These insects can crawl from the scalp of one person to another. They can also spread by indirect measures, including sharing combs, headscarves, hats, headphones, hair accessories, pillow covers, and bedding.


The female louse releases a sticky compound that helps it attach to an individual hair’s shaft. The female lays eggs that hatch within 6 to 9 days. Once they hatch, an immature form of louse called nymph is produced. These nymphs grow to mature adults in 9 to 12 days. Once they are mature, they can survive for up to 4 weeks. During this period, they can spread from one person to another. 

Risk Factors And Epidemiology

The risk of head lice is highest among preschool children who tend to play closely with each other. Even if a single child has a head lice infestation, it can spread to other children who play close to them. In the United States, head lice are most common among preschool or elementary children. An affected child can also spread head lice to their siblings or caretakers. 

Signs And Symptoms

When someone has a head lice infestation, the most frequent complaint is itching. Itching occurs as an allergic reaction to bites from head lice. If you or your child has an infestation for the first time, you may not feel itching for weeks. During this period, head lice mature into adults and grow in numbers. When itching begins, it can be mild in the initial period but may increase over time. Children who keep scratching their heads may cause minor breaks in their skin. This leads to a secondary risk of bacterial infections, but it is rare. Lice are visible on the scalp, and the hair stands on close inspection. 


Head lice can be diagnosed by closely examining the scalp and hair. The gold standard for identifying an active head lice infestation is to find a live louse or its nymph form. Live head lice can be seen crawling through the scalp or attached to hair strands. For this purpose, the recommended method is to lubricate hair with a conditioner and run a fine-toothed comb through them from the scalp to the end. If live head lice are present, they will be trapped between the comb’s tooth. Your doctor may also use Wood’s lamp to examine your hair to identify live nits. If they are very small in size, microscopic examination can also determine whether they are alive or not. Dead lice are most likely an indication of a previous infestation. 

Differential Diagnosis

Head lice need to be differentiated from dandruff, dust, or other forms of debris in your hair. They can be easily differentiated by their stickiness to individual hair strands. It should also be differentiated from other causes of itching to make sure there is no underlying skin condition.  


There are multiple treatment options available to treat an active head lice infestation. You can find non-prescription medications to kill lice. One of the most commonly used pesticides is pyrethrin. It is made from chrysanthemums flowers. Another synthetic form of this compound is also available, called permethrin. These products are safe to use in children over two years of age. A second treatment is often required 7 to 9 days after the first treatment for maximum effectiveness.


Home remedies are also used in many areas to kill head lice. One of the methods is wet combing. Hair is lubricated first with a conditioner or oil and then combed thoroughly with a fine comb. This needs to be done repeatedly over several weeks until no active lice are found. Other herbal techniques are also used, but their effectiveness is unclear. You should also wash your pillow covers, bedding, and head clothing items in hot water to get rid of lice.

Prescription medications are also available for lice treatment. These may include ivermectin, spinosad, malathion, and benzyl alcohol lotion. These medications can be used in children over the age of 6 months. Any medication should be used after consultation with your doctor. 


With appropriate treatment options, the prognosis of this condition is very good. Although you have to keep in mind that you or your child may get re-infected if you get in close contact with another infected person. It may take two or more weeks for complete treatment of head lice. Therefore, during this period and afterward, stay away from any possible sources of reinfection.  


It is difficult to prevent a head lice infestation among young children because they are always in close contact during school and other activities. Prevention can be done to a certain extent by avoiding sharing personal items such as headbands, combs, hair accessories, etc. Keeping your child away from other children in fear of head lice infestation is not an appropriate solution.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on May 20, 2023. 



Head lice: Diagnosis and treatment (aad.org)


CDC - Lice - Head Lice - General Information - Frequently Asked Questions (FAQs)