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InfectiousICD-10: B85.06-12 million infestations annually in U.S. children aged 3-11

Head Lice (Pediculosis)

Head lice are tiny parasitic insects (Pediculus humanus capitis) that infest the hair and scalp, feeding on human blood several times a day. Head lice infestations—medically called pediculosis capitis—are extremely common among school-age children and their families, with an estimated 6-12 million infestations occurring annually in the U.S. among children aged 3-11. While head lice do not transmit disease and are not a sign of poor hygiene, they cause significant itching, social stigma, and disruption to daily life.

Symptoms

Intense itching of the scalp, especially behind the ears and at the nape of the neck
Tickling feeling or sensation of something moving in the hair
Visible nits (lice eggs) firmly attached to hair shafts near the scalp
Visible live lice moving in the hair (though they move quickly and are hard to see)
Small red bumps or sores on the scalp, neck, and shoulders from scratching
Difficulty sleeping (lice are most active in the dark)

Causes

  • Direct head-to-head contact with an infested person (most common transmission)
  • Less commonly, sharing personal items such as hats, combs, brushes, or headbands
  • Contact with infested bedding, pillows, or upholstered furniture (less likely)
  • Lice cannot jump or fly—they spread by crawling from hair to hair

Risk Factors

  • School-age children (ages 3-11) and their household contacts
  • Girls and women (more commonly affected, likely due to hair contact behaviors)
  • Close contact activities (sleepovers, sports, camp)
  • Sharing personal items that touch the head

Diagnosis

  • Visual inspection of the scalp and hair for live lice and nits
  • Use of a fine-toothed lice comb (nit comb) on wet, conditioned hair to detect lice
  • Magnification with a bright light or Wood's lamp to identify nits close to the scalp
  • Distinguishing nits from dandruff, hair casts, or debris (nits are firmly attached and do not slide off)

Treatment

  • Over-the-counter pediculicides (permethrin 1% lotion or pyrethrin-based shampoo) as first-line treatment
  • Prescription treatments (ivermectin lotion, spinosad, malathion, benzyl alcohol) for resistant cases
  • Oral ivermectin for recurrent or hard-to-treat infestations
  • Manual nit removal with a fine-toothed comb after treatment
  • Repeat treatment after 7-10 days to kill newly hatched lice
  • Washing bedding and clothing in hot water (130°F/54°C) and drying on high heat

Prevention

  • Avoid head-to-head contact during play, sports, and sleepovers
  • Do not share combs, brushes, hats, scarves, or hair accessories
  • Teach children not to share personal items that contact the head
  • Regular head checks during school outbreaks
  • Tie long hair back or braid it to minimize contact opportunities

When to See a Doctor

  • Over-the-counter treatments do not eliminate the infestation after two treatments
  • The scalp becomes infected from excessive scratching
  • You are unsure whether the infestation is lice or another condition

Frequently Asked Questions

Related Conditions

Cellulitis

Infectious

Acne Vulgaris

Dermatological

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Medical Disclaimer: This content is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.

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