eMedicine Specialties > Emergency Medicine > Infectious Diseases

Lice: Differential Diagnoses & Workup

Author: Wayne Wolfram, MD, MPH, Clinical Associate Professor, Departments of Pediatrics, Children's Hospital and University of Cincinnati
Coauthor(s): Neil W Yoder, DO, Staff Physician, Department of Emergency Medicine, St Vincent Mercy Medical Center
Contributor Information and Disclosures

Updated: May 5, 2009

Differential Diagnoses

Anxiety
Bites, Insects
Impetigo
Scabies
Sexual Assault

Other Problems to Be Considered

Desquamated epithelial cells (dandruff)
Seborrheic scales
Hair root sheath casts

Workup

Other Tests

  • The diagnosis rests on the observation of eggs (nits), nymphs, or mature lice.
    • Observing lice is difficult. Nymphs and mature lice, despite being unable to hop or jump, can move rapidly through dry hair.  
    • Wetting the hair and using a fine toothed comb aid in observation.
    • Mature lice are 3-4 mm long (approximately the size of a sesame seed). Nits are much smaller—about 1 mm. The pubic louse is about the same length as the head or body louse but has a wider body.
    • The use of a magnifying glass and knowing where to look for lice (based upon the biology of each species as described above) assists diagnosis.
  • Nits are fluorescent under a Wood light.
  • Unlike dandruff and hair root sheath casts, nits are cemented to the hair and are difficult to remove.

More on Lice

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

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

  2. Burgess IF, Brown CM, Lee PN. Treatment of head louse infestation with 4% dimeticone lotion: randomised controlled equivalence trial. BMJ. Jun 18 2005;330(7505):1423. [Medline].

  3. Burgess IF, Lee PN, Matlock G. Randomised, controlled, assessor blind trial comparing 4% dimeticone lotion with 0.5% malathion liquid for head louse infestation. PLoS ONE. Nov 7 2007;2(11):e1127. [Medline].

  4. American Academy of Pediatrics. Pediculosis. In: Pickering, LK ed. 2003 Red Book: Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Il: AAP; 2003:463-467.

  5. Brown S, Becher J, Brady W. Treatment of ectoparasitic infections: review of the English-language literature, 1982-1992. Clin Infect Dis. Apr 1995;20 Suppl 1:S104-9. [Medline].

  6. Clore ER, Longyear LA. A comparative study of seven pediculicides and their packaged nit removal combs. J Pediatr Health Care. Mar-Apr 1993;7(2):55-60. [Medline].

  7. Drugs for head lice. Med Lett Drugs Ther. Jan 17 1997;39(992):6-7. [Medline].

  8. Gilbert DN, Moellering RC, Jr., Samde MA. The Sanford Guide to Antibiotic Therapy 1998. Dallas, Tex: Antimicrobial Therapy Inc; 1998:94-95.

  9. Halpern JS. Recognition and treatment of pediculosis (head lice) in the emergency department. J Emerg Nurs. Apr 1994;20(2):130-3. [Medline].

  10. Hart G. Risk profiles and epidemiologic interrelationships of sexually transmitted diseases. Sex Transm Dis. May-Jun 1993;20(3):126-36. [Medline].

  11. Heukelbach J, Feldmeier H. Ectoparasites--the underestimated realm. Lancet. Mar 13 2004;363(9412):889-91. [Medline].

  12. Huynh TH, Norman RA. Scabies and pediculosis. Dermatol Clin. Jan 2004;22(1):7-11. [Medline].

  13. Ibarra J, Hall DM. Head lice in schoolchildren. Arch Dis Child. Dec 1996;75(6):471-3. [Medline].

  14. Klaus S, Shvil Y, Mumcuoglu KY. Generalized infestation of a 3 1/2-year-old girl with the pubic louse. Pediatr Dermatol. Mar 1994;11(1):26-8. [Medline].

  15. Kristensen M, Knorr M, Rasmussen AM, et al. Survey of permethrin and malathion resistance in human head lice populations from Denmark. J Med Entomol. May 2006;43(3):533-8. [Medline].

  16. 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].

  17. Mumcuoglu KY, Meinking TA, Burkhart CN, et al. Head louse infestations: the "no nit" policy and its consequences. Int J Dermatol. Aug 2006;45(8):891-6. [Medline].

  18. Yoon KS, Gao JR, Lee SH, et al. Permethrin-resistant human head lice, Pediculus capitis, and their treatment. Arch Dermatol. Aug 2003;139(8):994-1000. [Medline].

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Further Reading

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Keywords

lice, louse, nits, pediculosis capitis, head lice, pediculosis corporis, body lice, pediculosis pubis, pubic lice, crabs, Pediculus humanus capitis, Pediculus humanus corporis, Pthirus pubis, lice infestation

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Contributor Information and Disclosures

Author

Wayne Wolfram, MD, MPH, Clinical Associate Professor, Departments of Pediatrics, Children's Hospital and University of Cincinnati
Wayne Wolfram, MD, MPH is a member of the following medical societies: American Academy of Emergency Medicine, American Academy of Pediatrics, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

Neil W Yoder, DO, Staff Physician, Department of Emergency Medicine, St Vincent Mercy Medical Center
Neil W Yoder, DO is a member of the following medical societies: American College of Emergency Physicians and Emergency Medicine Residents Association
Disclosure: Nothing to disclose.

Medical Editor

Edmond A Hooker II, MD, DrPH, FAAEM, Assistant Professor, Department of Health Services Administration, Xavier University; Associate Clinical Professor, Department of Emergency Medicine, University of Louisville; Assistant Clinical Professor, Department of Emergency Medicine, Wright State University
Edmond A Hooker II, MD, DrPH, FAAEM is a member of the following medical societies: American Academy of Emergency Medicine, American Public Health Association, Society for Academic Emergency Medicine, and Southern Medical Association
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

Jonathan Adler, MD, Attending Physician, Department of Emergency Medicine, Massachusetts General Hospital; Division of Emergency Medicine, Harvard Medical School
Jonathan Adler, MD is a member of the following medical societies: American Academy of Emergency Medicine and Society for Academic Emergency Medicine
Disclosure: eMedicine.com, Inc. Consulting fee Consulting

 
 
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