Continually Updated Clinical Reference
 
 
  All Sources     eMedicine     Medscape     Drug Reference     MEDLINE
 
eMedicine - Pediculosis : Article by

Quick Find
Authors & Editors
Introduction
Clinical
Differentials
Workup
Treatment
Medication
Follow-up
Miscellaneous
Multimedia
References

Related Articles
Abortion, Inevitable




Patient Education
Parasites and Worms Center

Lice Overview

Lice Causes

Lice Symptoms

Lice Treatment

Crabs Overview


AUTHOR AND EDITOR INFORMATION

Section 1 of 11 Click here to go to the next section in this topic  

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 is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology

Coauthor(s): Abdul-Ghani Kibbi, MD, Chairman and Professor, Department of Dermatology, American University of Beirut Medical Center, Lebanon

Editors: 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; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Jeter (Jay) Pritchard Taylor III, MD, Compliance Officer, Attending Physician Emergency Medicine Residency, Department of Emergency Medicine, Palmetto Richland Memorial Hospital, University of South Carolina; 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; Pamela L Dyne, MD, Associate Professor, Program Director, Department of Medicine, Division of Emergency Medicine, University of California at Los Angeles School of Medicine

Author and Editor Disclosure

Synonyms and related 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

INTRODUCTION

Section 2 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page Click here to go to the next section in this topic  

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).

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

Section 3 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page Click here to go to the next section in this topic  

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


DIFFERENTIALS

Section 4 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page Click here to go to the next section in this topic  

Abortion, Inevitable

Other Problems to be Considered

Dandruff
Hair casts
Piedra


WORKUP

Section 5 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page Click here to go to the next section in this topic  

Lab Studies

Other Tests

  • For the diagnosis of P capitis, the use of a louse comb is more efficient than direct visual examination of the scalp. Nits that are within 6 mm from the scalp are usually viable and are opalescent, whereas eggs that have hatched are white. Examine nits and lice under the microscope.
  • Slit-lamp examination may reveal pubic lice on eyelashes and eyebrows.
  • Live nits are fluorescent white when illuminated with a Wood lamp; empty nits are fluorescent gray.


TREATMENT

Section 6 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page Click here to go to the next section in this topic  

Emergency Department Care

  • Nits are best removed with a very fine comb.
  • Soaking the hair in a solution of equal parts water and white vinegar and then wrapping the wet scalp in a towel for at least 15 minutes may facilitate removal.
  • Treat all family members.
  • Discard infested clothing or wash in very hot water.
  • Evaluate for other STDs.


MEDICATION

Section 7 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page Click here to go to the next section in this topic  

The goal of therapy is to eliminate lice and eggs.

Linen, clothing, and other materials may be treated with hot water washing.

Eyelash infestation can be treated effectively with petrolatum ointment (eg, Vaseline).

Drug Category: Pediculicides

Chemical pediculicides are the mainstay of therapy. Treatment should be repeated in 7-10 days (the time needed for the eggs to hatch) because nits are less effectively killed than adults.

All contacts should be treated simultaneously.

Resistance to pediculicides has increased over recent years. Therapeutic agents can be rotated to slow the emergence of resistance.

Drug NamePermethrin 5% (Elimite) or 1% (Nix) lotion
DescriptionDOC, especially for infants >2 mo and small children. More effective than crotamiton in treating symptoms and reducing chances of secondary bacterial infection.
Even after successful treatment, postscabietic nodules and pruritus may persist for mo.
Adult DoseApply topically to affected area; leave 5-10 min, then rinse
Pediatric DoseAdminister as in adults
ContraindicationsDocumented hypersensitivity
InteractionsNone reported
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
PrecautionsMay exacerbate redness, swelling, and itching, at least temporarily

Drug NameLindane 1% shampoo (Kwell)
DescriptionStimulates nervous system of parasite, causing seizures and death. Second-line treatment if other agents fail or are not tolerated. Not very safe in children due to transcutaneous absorption leading to neurotoxicity. Overall, permethrin is a safer choice.
Adult DoseShampoo: Apply to dry head or pubic hair and surrounding areas; allow to set for 4 min, then lather for 4 min and rinse; repeat in 7 d prn
Pediatric DoseAdminister as in adults
ContraindicationsDocumented hypersensitivity; neonates; acutely swollen skin or Norwegian scabies
InteractionsOil-based hairdressings may increase toxicity of lindane
PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
PrecautionsCaution if history of seizures; do not apply to eyes, face, or mucous membranes; penetrates human skin and may cause CNS toxicity in young children, seizures have occurred after inappropriate use or ingestion

Drug NamePyrethrin/Piperonyl butoxide shampoo (RID Mousse, RID Shampoo, A-200)
DescriptionTreatment of P humanus infestations. Stimulates nervous system, causing seizures and death of parasite.
Adult DoseApply shampoo to dry hair and allow to set for 10 min before rinsing; repeat in 1 wk prn
Pediatric DoseAdminister as in adults
ContraindicationsDocumented hypersensitivity to product or Compositae plants
InteractionsNone reported
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
PrecautionsDo not apply to eyes, face, or mucous membranes

Drug NameMalathion (Ovide)
DescriptionApproved by FDA to treat head lice. Irreversible cholinesterase inhibitor that is hydrolyzed and, therefore, detoxified rapidly by mammals but not by insects; ovicidal and pediculicidal. Binds to hair and provides some residual protection after therapy. Available as 0.5% and 1% aqueous-based lotions.
Adult DoseApply lotion to dry hair; leave on 8-12 h, rinse; repeat in 7 d prn
Pediatric Dose<2 years: Not recommended
>2 years: Administer as in adults
ContraindicationsDocumented hypersensitivity
InteractionsNone reported; however, potential for interaction with aminoglycosides and antimyasthenics
Pregnancy
PrecautionsContains flammable alcohol; do not expose lotion or wet hair to open flame or electric heat, eg, hair dryers (allow hair to dry naturally and uncovered following application); avoid contact with eyes (flush eyes immediately with water if contact)

Drug NameIvermectin (Stromectol)
DescriptionBinds selectively with glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing cell death. Half-life is 16 h; metabolized in liver. DOC for onchocerciasis and strongyloidiasis. Recently shown to be effective against pediculosis but not yet approved by FDA. Not effective against nits.
Adult Dose150-200 mcg/kg/d PO as single dose; alternatively, 12 mg PO as single dose; may repeat in 1 wk prn
Pediatric Dose<5 years: Not established and not recommended
>5 years: 0.2 mg/kg PO as single dose; alternatively, administer as in adults
ContraindicationsDocumented hypersensitivity
InteractionsMay interact with other ligand-gated chloride channels, such as those gated by GABA
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
PrecautionsTreat mothers who intend to breastfeed only when risk of delayed treatment outweighs possible risks to the newborn caused by ivermectin excretion in milk
Repeat courses of therapy may be required in immunocompromised patients
May cause nausea, vomiting, and mild CNS depression; may cause drowsiness


FOLLOW-UP

Section 8 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page Click here to go to the next section in this topic  

Further Outpatient Care

  • Shaving of the scalp or body hair eradicates lice; however, this is not cosmetically acceptable for most patients.
  • Wet combing or application of diluted vinegar or commercial preparations of 8% formic acid may help in the removal of nits or at least make the combing easier. Plastic or the sturdier metal nit combs may be used.
  • Multiple lice suffocation agents have been advocated, but most have not been scientifically evaluated. These include Vaseline; petroleum jelly; oils; mayonnaise; and a dry-on, suffocation-based pediculicide lotion (DSP lotion).
  • Treatment of the patient's environment is important.
    • Fomites (clothes, towels, beddings, hats, children's stuffed animals) should be washed in hot water, machine-dried, ironed, or dry cleaned. Temperature exceeding 131°F (55°C) for more than 5 minutes kills eggs, nymphs, and mature lice.
    • Combs are hair brushes should be discarded, soaked in very hot water (>131°F or 55°C), or treated with pediculicides.

Deterrence/Prevention

  • All household members should be examined and treated at the same time if infested.
  • Safe sex practices may decrease the risk of STDs.

Complications

  • Persistent pruritus
  • Secondary bacterial infection

Prognosis

  • Pediculosis has more than a 90% cure rate with appropriate treatment.
  • Treatment failures are the result of improper application of pediculicides, noncompliance, reinfestation, or drug resistance.

Patient Education


MISCELLANEOUS

Section 9 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page Click here to go to the next section in this topic  

Medical/Legal Pitfalls

  • Lindane (Kwell) should be properly used. Seizure may result from abnormal absorption and gross overuse of the product.

Special Concerns

  • Pubic lice in children may be an indication of sexual abuse.


MULTIMEDIA

Section 10 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page Click here to go to the next section in this topic  

Media file 1:  Pthirus pubis (pubic or "crab" louse).
Click to see larger pictureClick to see detailView Full Size Image
Media type:  Photo


REFERENCES

Section 11 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page

  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. 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].
  6. 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].
  7. Burkhart CG, Burkhart CN. Oral ivermectin for Phthirus pubis. J Am Acad Dermatol. Dec 2004;51(6):1037; author reply 1037-8. [Medline].
  8. Burkhart CG, Burkhart CN. Safety and efficacy of pediculicides for head lice. Expert Opin Drug Saf. Jan 2006;5(1):169-79. [Medline].
  9. CDC. Unintentional topical lindane ingestions--United States, 1998-2003. MMWR Morb Mortal Wkly Rep. Jun 3 2005;54(21):533-5. [Medline].
  10. Hart G. Factors associated with pediculosis pubis and scabies. Genitourin Med. Oct 1992;68(5):294-5. [Medline].
  11. Jones KN, English JC. Review of common therapeutic options in the United States for the treatment of pediculosis capitis. Clin Infect Dis. Jun 1 2003;36(11):1355-61. [Medline].
  12. 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].
  13. Ko CJ, Elston DM. Pediculosis. J Am Acad Dermatol. Jan 2004;50(1):1-12; quiz 13-4. [Medline].
  14. Lebwohl M, Clark L, Levitt J. Therapy for head lice based on life cycle, resistance, and safety considerations. Pediatrics. May 2007;119(5):965-74. [Medline].
  15. Mahe A, Prual A, Konate M, Bobin P. Skin diseases of children in Mali: a public health problem. Trans R Soc Trop Med Hyg. Sep-Oct 1995;89(5):467-70. [Medline].
  16. Meinking TL. Clinical update on resistance and treatment of Pediculosis capitis. Am J Manag Care. Sep 2004;10(9 Suppl):S264-8. [Medline].
  17. Meinking TL, Serrano L, Hard B. Comparative in vitro pediculicidal efficacy of treatments in a resistant head lice population in the United States. Arch Dermatol. Feb 2002;138(2):220-4. [Medline].
  18. 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].
  19. Nash B. Treating head lice. BMJ. Jun 7 2003;326(7401):1256-7. [Medline].
  20. Pearlman DL. A simple treatment for head lice: dry-on, suffocation-based pediculicide. Pediatrics. Sep 2004;114(3):e275-9. [Medline].
  21. Roberts RJ, Burgess IF. New head-lice treatments: hope or hype?. Lancet. Jan 1-7 2005;365(9453):8-10. [Medline].
  22. Routh HB, Mirensky YM, Parish LC. Ectoparasites as sexually transmitted diseases. Semin Dermatol. Dec 1994;13(4):243-7. [Medline].
  23. 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].
  24. 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].
  25. 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].
  26. 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].
  27. Yoon KS, Gao JR, Lee SH. Permethrin-resistant human head lice, Pediculus capitis, and their treatment. Arch Dermatol. Aug 2003;139(8):994-1000. [Medline].

Pediculosis excerpt

Article Last Updated: Jun 3, 2008