eMedicine Specialties > Emergency Medicine > Infectious Diseases

Pediculosis

Author: Nelly Rubeiz, MD, Consulting Staff, Department of Dermatology, American University of Beirut Medical Center; Associate Professor, Department of Dermatology, American University of Beirut, Lebanon
Coauthor(s): Abdul-Ghani Kibbi, MD, Chairman and Professor, Department of Dermatology, American University of Beirut Medical Center, Lebanon
Contributor Information and Disclosures

Updated: May 5, 2009

Introduction

Background

Infestation with lice is referred to as pediculosis. Lice are ectoparasites that live on the body. The 3 types of lice that parasitize humans are Pediculus humanus capitis (head louse), Pediculus humanus corporis (body louse), and Pthirus pubis (pubic louse).


<EM>Pthirus pubis</EM> (pubic or "crab" louse).

Pthirus pubis (pubic or "crab" louse).

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<EM>Pthirus pubis</EM> (pubic or "crab" louse).

Pthirus pubis (pubic or "crab" louse).


The disease is spread from person to person by close physical contact or through fomites (eg, combs, clothes, hats, linens). Overcrowding encourages the spread of lice. The body louse is the vector of typhus, trench fever, and relapsing fever.

Pathophysiology

Lice have claws on their legs that are adapted for feeding and clinging to hair or clothing. Head and body lice are similarly shaped, but the head louse is smaller. The pubic or crab louse is quite distinct in appearance; it has pincerlike claws resembling those of sea crabs. Lice are blood-sucking insects. They feed on human blood several times daily. They stay close to the skin for moisture, food, and warmth. They move freely and quickly, which explains their ease of transmission. A fertilized female louse lays about 10 eggs a day for up to a month until it dies.

The eggs (nits) are attached to the hair shaft, close to the skin surface, where the temperature is optimal for incubation. The eggs hatch in about 6-10 days. Nits are cemented to the hair shaft with chitin and are very difficult to remove. Nits can survive for up to 10 days away from the human host.

Pubic lice may be found on the short hairs of the body, areolar hair, axillary hair, beard, scalp margins, eyebrows, and eyelashes, in addition to pubic hair.

Body lice and their eggs are predominantly found on clothing and should be looked for in the seams of clothes.

Frequency

United States

Pediculosis affects 6-12 million people annually. P capitis is common among school children. Head lice are very rare among African Americans; this may be due to the twisted nature of the hair shaft and the use of hair pomades. Infestation with P pubis is a sexually transmitted disease (STD).

International

Pediculosis has a worldwide distribution and is endemic both in developing and developed countries. For example, P capitis was found in 9.6% of adolescent schoolboys in Saudi Arabia.1 In Mali, the prevalence of head lice in children was 4.7%.2 Among attendees of a STD clinic in South Australia, pubic lice were found in 1.7% of men and 1.1% of women.3 P corporis is now uncommon in developed countries except in the homeless.4

Sex

Pediculosis is more common in females than in males.

Age

Pediculosis can affect any age group.

  • P capitis is most frequent in children, especially young and adolescent females. The peak incidence is from age 5-11 years. Direct head-to-head contact is the most common mode of transmission.
  • P pubis is most common in sexually active adults.

Clinical

History

  • Itching is the most common symptom of the infestation.
  • Scratching may cause inflammation and a secondary bacterial infection.

Physical

  • P capitis
    • Head lice and nits are found most often on the occiput, posterior neck, and behind the ears.
    • Excoriations on the scalp, posterior neck, and upper back; bite reactions; secondary bacterial infection; and cervical lymphadenopathy are common manifestations.
    • Eyelashes may be involved.
    • Conjunctivitis may be seen.
  • P corporis
    • Adult lice and nits are found in clothing seams.
    • Uninfected bites present as erythematous papules, 2-4 mm in diameter, with an erythematous base.
  • P pubis
    • Pubic hair is the most common site. The crab louse is found firmly attached to the base of the pubic hair. Nits may also be found.
    • Pubic lice may spread to hair around the anus, abdomen, axillae, chest, and eyelashes.
    • Bluish grey macules, or maculae cerulea, may be seen on the abdomen or thighs and are secondary to the bites of the crab louse.

Causes

  • Risk factors
    • Overcrowding
    • Poor hygiene
    • Debilitated and malnourished individuals
    • Sexual promiscuity

More on Pediculosis

Overview: Pediculosis
Differential Diagnoses & Workup: Pediculosis
Treatment & Medication: Pediculosis
Follow-up: Pediculosis
Multimedia: Pediculosis
References
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References

  1. Bahamdan K, Mahfouz AA, Tallab T, et al. Skin diseases among adolescent boys in Abha, Saudi Arabia. Int J Dermatol. Jun 1996;35(6):405-7. [Medline].

  2. Leung AK, Fong JH, Pinto-Rojas A. Pediculosis capitis. J Pediatr Health Care. Nov-Dec 2005;19(6):369-73. [Medline].

  3. Foucault C, Ranque S, Badiaga S. Oral ivermectin in the treatment of body lice. J Infect Dis. Feb 1 2006;193(3):474-6. [Medline].

  4. Elston DM. Treating pediculosis--those nit-picking details. Pediatr Dermatol. Jul-Aug 2007;24(4):415-6. [Medline].

  5. Benzyl alcohol lotion 5% [package insert]. Atlanta, GA: Sciele Pharma Inc; 2009. [Full Text].

  6. Brand RM, Charron AR, Brand RE. Decreasing malathion application time for lice treatment reduces transdermal absorption. Int J Pharm. Sep 14 2005;301(1-2):48-53. [Medline].

  7. Burkhart CG. Relationship of treatment-resistant head lice to the safety and efficacy of pediculicides. Mayo Clin Proc. May 2004;79(5):661-6. [Medline].

  8. Burkhart CG, Burkhart CN. Oral ivermectin for Phthirus pubis. J Am Acad Dermatol. Dec 2004;51(6):1037; author reply 1037-8. [Medline].

  9. Burkhart CG, Burkhart CN. Safety and efficacy of pediculicides for head lice. Expert Opin Drug Saf. Jan 2006;5(1):169-79. [Medline].

  10. CDC. Unintentional topical lindane ingestions--United States, 1998-2003. MMWR Morb Mortal Wkly Rep. Jun 3 2005;54(21):533-5. [Medline].

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  13. Kennedy D, Hurst V, Konradsdottir E, Einarson A. Pregnancy outcome following exposure to permethrin and use of teratogen information. Am J Perinatol. Feb 2005;22(2):87-90. [Medline].

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  17. Meinking TL. Clinical update on resistance and treatment of Pediculosis capitis. Am J Manag Care. Sep 2004;10(9 Suppl):S264-8. [Medline].

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  19. Meinking TL, Vicaria M, Eyerdam DH, Villar ME, Reyna S, Suarez G. A randomized, investigator-blinded, time-ranging study of the comparative efficacy of 0.5% malathion gel versus Ovide Lotion (0.5% malathion) or Nix Crème Rinse (1% permethrin) used as labeled, for the treatment of head lice. Pediatr Dermatol. Jul-Aug 2007;24(4):405-11. [Medline].

  20. Nash B. Treating head lice. BMJ. Jun 7 2003;326(7401):1256-7. [Medline].

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  22. Roberts RJ, Burgess IF. New head-lice treatments: hope or hype?. Lancet. Jan 1-7 2005;365(9453):8-10. [Medline].

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  24. Silva L, Alencar Rde A, Madeira NG. Survey assessment of parental perceptions regarding head lice. Int J Dermatol. Mar 2008;47(3):249-55. [Medline].

  25. Speare R, Canyon DV, Cahill C, Thomas G. Comparative efficacy of two nit combs in removing head lice (Pediculus humanus var. capitis) and their eggs. Int J Dermatol. Dec 2007;46(12):1275-8. [Medline].

  26. Takano-Lee M, Edman JD, Mullens BA. Transmission potential of the human head louse, Pediculus capitis (Anoplura: Pediculidae). Int J Dermatol. Oct 2005;44(10):811-6. [Medline].

  27. Willems S, Lapeere H, Haedens N. The importance of socio-economic status and individual characteristics on the prevalence of head lice in schoolchildren. Eur J Dermatol. Sep-Oct 2005;15(5):387-92. [Medline].

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Further Reading

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Keywords

pediculosis, lice, lice infestation, Pediculus humanus capitis, head louse, head lice, Pediculus humanus corporis, body louse, body lice, Pthirus pubis, pubic louse, pubic lice, lice eggs, nits, typhus, trench fever, relapsing fever, cervical lymphadenopathy, conjunctivitis, human immunodeficiency virus, HIV, syphilis, gonorrhea, chlamydia, genital herpes, trichomonas

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Contributor Information and Disclosures

Author

Nelly Rubeiz, MD, Consulting Staff, Department of Dermatology, American University of Beirut Medical Center; Associate Professor, Department of Dermatology, American University of Beirut, Lebanon
Nelly Rubeiz, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology
Disclosure: Nothing to disclose.

Coauthor(s)

Abdul-Ghani Kibbi, MD, Chairman and Professor, Department of Dermatology, American University of Beirut Medical Center, Lebanon
Disclosure: none None None

Medical Editor

David A Peak, MD, Assistant Residency Director of Harvard Affiliated Emergency Medicine Residency, Attending Physician, Massachusetts General Hospital; Consulting Staff, Department of Hyperbaric Medicine, Massachusetts Eye and Ear Infirmary
David A Peak, MD is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, Society for Academic Emergency Medicine, and Undersea and Hyperbaric Medical Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Jeter (Jay) Pritchard Taylor III, MD, Compliance Officer, Attending Physician, Emergency Medicine Residency, Department of Emergency Medicine, Palmetto Health Richland, University of South Carolina; Medical Director, Department of Emergency Medicine, Palmetto Health Baptist
Jeter (Jay) Pritchard Taylor III, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Pamela L Dyne, MD, Professor of Clinical Medicine/Emergency Medicine, David Geffen School of Medicine at UCLA; Attending Physician, Department of Emergency Medicine, Olive View-UCLA Medical Center
Pamela L Dyne, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

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