Dr. Lauren Livelo 22 Jun 2022

Pediculosis refers to is the infestation of humans by lice. It affects many people worldwide and does not discriminate against gender or socioeconomic classes. There are three species of lice that can infest humans: the head louse, the body louse, and the crab louse. Lice cannot jump or fly. Transmission requires close contact, and symptoms usually take 2-6 weeks to appear.

Pediculosis capitis (Head lice)

Head lice are caused by Pediculosis humanus capitis, or the head louse. It is common in the pediatric population (ages 3-12). It affects the scalp, especially the occipital area, as well as the area behind the ears. Some people do not feel any symptoms and become carriers, while some complain of pruritus (itch). People can be infected by direct transmission, or more rarely, by fomite transmission through the use of brushes, hair accessories, beddings, pillows, and other headgear.

In order to diagnose head lice, one should look for the presence of live lice or nits (egg capsules) on the scalp. These usually can be seen with the naked eye. New eggs are usually located near the scalp, while those that have hatched are more distant from the scalp. One can also find live lice or nits by wetting the hair with water and conditioner, then combing the hair with a nit comb. It is important to check all members of the household, as pediculosis capitis can be highly contagious.

If not treated properly, secondary bacterial infections (pyoderma) of the scalp can be a source of complications.

Pediculosis corporis (Body lice)

Body lice are caused by Pediculosis humanus humanus. These lice appear larger than head lice and usually lay eggs in clothing or bedding, then move to the skin to feed. Those affected usually experience pruritus and may have some excoriations on the body due to scratching. The most commonly affected populations include homeless individuals, those who live in crowded areas, and those with poor hygiene. Body lice can be spread by direct contact with those infected, but some cases have also shown fomite transmission via clothing, towels, and bedding. Body lice are diagnosed by careful examination of the seams and folds of clothing for the presence of nits.

There are several diseases that can be transmitted by the body louse. These include typhus, murine typhus, trench fever, and relapsing fever. Secondary bacterial infections may also occur.

Pediculosis pubis (Crab lice / Pthirus pubis)

Crab lice are caused by P. pubis infestation. They are most commonly found in the pubic and perianal region, but some cases have reported that crab lice can also reside in the axillae, eyebrows, eyelashes (Phthiriasis palpebrarum), and in beards. Lice can be transmitted via contaminated clothing, towels, and bedding. It can also be transmitted via sexual contact.

Diagnosis of crab lice is usually made clinically. Identification of lice in pubic hair confirms the diagnosis. Once diagnosed, it is important to contact previous sexual partners, as they can also be affected.


Pharmacologic therapy for Pediculosis

Pediculicides are still the best treatment option for pediculosis. These include:

  • Permethrin
  • Malathion
  • Lindane
  • Benzyl alcohol 5% lotion
  • Topical or oral ivermectin
  • Spinosad

There are specific instructions on how to use these medications; therefore, it is better to consult with your physician for proper diagnosis and treatment.

Non-pharmacologic therapy for Pediculosis

  • Apply moisturizer or conditioner on wet hair, and comb the lice and nits out every 3 days for two weeks.
  • Wash combs, brushes, and other head/hair accessories in very hot water (65°C).
  • Vacuum floors, carpets, upholstery, and other furniture.
  • Clothing and bedding should be machine washed in hot water (at least 52°C for 30 minutes) and dried in high heat.

Take-Home Messages

Lice infestations can cause feelings of embarrassment, as well as loss of school days for infected children. Parents and patients who are educated about the need for all members of the household to get examined and treated can help decrease the cases of lice infestation in schools. When suspecting a lice infestation, it is better to consult with a physician regarding proper treatment and management.

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About the Author:
Dr. Lauren Livelo is a board-certified dermatologist from the Philippines. She has a degree in Medicine from the University of the East Ramon Magsaysay Memorial Medical Center, and has completed her dermatology residency training in the Research Institute for Tropical Medicine. Aside from her private practice, she enjoys writing about skin care and diseases of the skin.


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  • CDC - DPDx - Pediculosis. (n.d.). Centers for Disease Control and Prevention. Retrieved June 20, 2022, from
  • Kang, S. (2018). Fitzpatrick’s Dermatology, Ninth Edition, 2-Volume Set (EBOOK). McGraw Hill Professional.
  • Pediculosis and Scabies: A Treatment Update. (n.d.). AAFP Home | American Academy of Family Physicians. Retrieved June 20, 2022, from

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