Summary

Head lice infestation (Pediculosis Capitis) is caused by Pediculus humanus capitis, a small parasitic insect that lives on the human scalp and feeds on blood. Head lice are extremely common in school-age children (4-11 years) and spread primarily through Direct Head-to-Head Contact. Infestation does NOT indicate poor hygiene. The main symptom is Itching (Pruritus) of the scalp, though many children are asymptomatic. Diagnosis is made by identifying Live Lice (Definitive) or Eggs (Nits) attached to hair shafts (less than 1cm from scalp = Likely active). Detection Combing (Wet combing with a fine-toothed nit comb) is the best diagnostic method. Treatment options include Physical Methods (Wet combing – "Bug Busting") or Topical Insecticides/Dimeticone. Repeated applications are usually needed to kill newly hatched lice. Close contacts should be checked, And clothing/bedding do not require special treatment. [1,2,3]

Clinical Pearls

"Live Lice = Active Infestation": Finding live lice confirms active infestation. Eggs alone may be old.

"Eggs less than 1cm from Scalp = Likely Active": Eggs further away have likely already hatched or are non-viable.

"Wet Combing Diagnoses and Treats": Detection combing is better than visual inspection. Can also be used as treatment.

"Lice Don't Jump": Spread by Direct Head-to-Head contact, NOT by jumping, Sharing hats, Or bedding (Rare).

Pediculus humanus capitis (Head Louse)

Life Cycle

Implication for Treatment: Need to re-treat at ~7 days to kill newly hatched nymphs before they mature and lay eggs.

Key Guidelines

What are Head Lice?

Head lice are tiny insects that live on the scalp and feed on blood. They are very common in children, Especially school-age kids. They spread by close head-to-head contact (Not by jumping or sharing hats).

Do head lice mean my child is dirty?

No. Head lice have nothing to do with cleanliness. They can affect anyone.

What are the signs?

• Itching of the scalp.
• Feeling something moving in the hair.
• Seeing tiny insects or eggs ("Nits") attached to hair.

How do I check?

The best way is Detection Combing (Wet Combing):

1. Wash hair and apply lots of conditioner.
2. Comb through with a fine-toothed nit comb.
3. Wipe the comb on white paper and look for lice.

How are they treated?

Option 1: Wet Combing ("Bug Busting"): Comb through conditioned hair every 3-4 days for 2 weeks to remove lice.

Option 2: Lotions: Apply a product like Dimeticone (Hedrin) to dry hair, Leave on, Wash out. Repeat after 7 days.

What about the rest of the family?

Check everyone in the household. Only treat those with live lice.

Does my child need to stay off school?

No. Your child can go to school once treatment has started.

Common Exam Questions

1. Diagnostic Method: "What is the best method to diagnose head lice?"
   • Answer: Detection Combing (Wet Combing) with a fine-toothed nit comb.
2. First-Line Treatment: "What is a first-line topical treatment for head lice?"
   • Answer: Dimeticone (e.g., Hedrin 4% Lotion). Physical action, No resistance.
3. Repeat Treatment: "Why is a second treatment application needed after 7 days?"
   • Answer: To kill Newly Hatched Nymphs from eggs that survived the first treatment (Eggs are more resistant than lice).
4. Transmission: "How are head lice primarily transmitted?"
   • Answer: Direct Head-to-Head Contact. Lice do NOT jump or fly.

Viva Points

• Eggs less than 1cm from Scalp: Likely viable. >1cm: Likely hatched/Dead.
• No Nit Policies Unnecessary: Exclusion not needed.
• Resistance to Permethrin Common: Dimeticone preferred.
• Doesn't Indicate Poor Hygiene: Important to reassure parents.

Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.