Treatment of Head Lice

C. H. Hong, MD, FRCPC
Department of Dermatology and Skin Science, University of British Columbia, and Skinfit MD Clinic, Vancouver, Canada

Head Lice

An estimated 1 in 10 children in Canada will be affected by a lice infestation this year and it is more common worldwide than the common cold. Head lice infestations, i.e., Pediculosis humanus capitis, are the most common type, which can occur worldwide and affect people of all ages and socioeconomic groups. Lice are wingless, bloodsucking insects. They are difficult to see because they are about the size of a sesame seed and they adapt to take on the color of their surroundings.

• Occurs most commonly in school-aged children, especially girls between 3 and 11 years of age.
• Is often epidemic. Most common places for outbreaks include schools, day cares, and play groups.
• Personal hygiene and socioeconomic status are not related to the likelihood of developing lice infestation.
• Not known to transmit bloodborne diseases.
• Spread though close head-to-head contact or through fomites (inanimate objects) that come into contact with the infested scalp and then are shared (e.g., combs, brushes, and hats).

Clinical Manifestations and Diagnosis

Head lice are typically confined to the scalp, and while itching is the main symptom of lice infestation, the lice themselves are not itchy and the bites are generally painless. Itching is caused by the body’s immune reaction to the saliva injected into the skin at the time of the blood meal. Redness and scaling may also be seen in the scalp as can small, itchy bumps on the posterior neck. Enlargement of lymph glands in the neck can be occasionally seen.

Diagnosis can be made ONLY by identification of a living louse. Nits or eggs are often empty shells and not an indication of an active infestation. Nits are also often mistaken for dandruff, sand or dirt, or dried hair gel.

Myths and Facts

Myths about head lice are abundant and belief in these myths is often why treatments are not used properly and why people believe their lice treatment has failed. Some common myths include:

• Myth: All children with lice scratch or itch.
  Fact: Initial infestation may produce no signs or symptoms for 4–6 weeks; only 1 in 3 children will complain of itching.


• Myth: Lice jump or fly from head to head.
  Fact: Lice can be dislodged from hair by air movements giving the appearance of flying.


• Myth: Lice live in carpets, beds, clothes, and sofas.
  Fact: Lice can only live for 24 hours away from a human host.


• Myth: Lice die immediately after treatment.
  Fact: Lice may take several hours to die following treatment.


• Myth: One treatment is enough.
  Fact: Due to loss of residual activity of pediculicides, two treatments, 7 days apart, are recommended to kill newly hatched nymphs.


• Myth: Permethrin based products are 100% ovicidal.
  Fact: Permethrin kills 70% of eggs with one treatment.


• Myth: Everyone in the family should be treated.
  Fact: Only those with a proven infestation should be treated, although everyone should be checked daily to weekly.


• Myth: Head lice prefer long or dirty hair.
  Fact: Lice do not care about hair length or cleanliness.

Treatment Options

There are many proposed “natural” and alternative cures for treating head lice including various oils (e.g., tea tree oil), petroleum jelly, peanut butter, and mayonnaise; however, the effectiveness of most are dubious. There are no clinical studies to demonstrate effectiveness of these agents and many are messy and difficult to use. Most patients will need to be treated with a commercial product designed to kill lice. Most of these are available over-the-counter and work by attacking the central nervous system of the louse. No pediculicide is 100% ovicidal. In order to achieve maximum effectiveness, the pediculicide needs to be applied to dry or nearly dry hair. It should be saturated to allow sufficient pediculicide to penetrate lice and nits and left on for the entire recommended time.

Permethrin 1% cream rinse (Nix®/Kwellada-P^®)

• Wash hair with conditioner-free shampoo and towel dry until hair is almost dry; then apply at least 25ml, and up to 50ml for thick or long hair, to hair and scalp especially behind the ears and the nape of the neck.
• Leave product on for 10 minutes then rinse with cool water over a sink (not in a shower or bath).
• Comb wet hair with nit comb to remove any dying lice and nits.
• A second treatment in 7 days should be carried out for maximum efficacy.
• There is minimal systemic absorption and low risk for toxicity.
• It is contraindicated in patients with chrysanthemum allergy.

Synergized pyrethrins (R & C^® shampoo)

• Apply to dry hair and scalp, especially behind the ears and the nape of the neck. Hair must be completely dry.
• Leave on 10 minutes, then add water to form lather. Rinse with cool water over a sink. Do not use conditioner.
• A second treatment in 7 days should be carried out for maximum efficacy.
• There is low risk of toxicity.
• Do not use if known allergy/sensitivity to chrysanthemum or ragweed.

Lindane shampoo 1%

• It is inexpensive.
• Apply to dry hair, leave on for 5 minutes and rinse with cool water over a sink (not in a shower or bath).
• Comb wet hair with nit comb to remove any dying lice and nits.
• Concern re: neurotoxicity with high dose or repeated exposure
• Contraindicated in neonates, young children (< 2 years of age), pregnant women, and nursing mothers or those with a history of seizures.
• Resistance has been seen for more than 2 decades.

Regardless of the type of treatment recommended, patients should be encouraged to use a nit comb (i.e., a fine toothed metal comb such as the LiceMeister^® comb), on wet hair to manually remove the nits, which can become cemented to the hair shafts. Treated patients should also be monitored for reinfestation.

Fomite Control

Following treatment, all clothing should be machine laundered and dried in the dryer (hot cycle). In addition, bed linens, towels, stuffed animals, and any headgear should be cleaned. Clothing that cannot be washed can be dry cleaned or sealed in a bag for 2 weeks. Combs and brushes can be covered in the pediculicide and then washed in hot water for 20 minutes; alternatively they can be soaked in a disinfectant solution (e.g., 2% Lysol^® for 1 hour). All interior areas should also be cleaned and vacuumed to remove any shed hairs.

Reasons for Failure of Treatment

• Wrong diagnosis
• Poor adherence / improper use of chemical lice treatment (e.g., applied to wet hair, insufficient product applied)
• Inadequate time to evaluate treatment (lice do not die on contact with product)
• Poor manual removal of nits
• New exposure to lice (re-infestation)
• Not repeating treatment 1 week later

Conclusion

Head lice are a common and embarrassing problem with many good treatments. Patients should be appropriately counseled to minimize spread of infestation and then advised on appropriate topical treatments. For further information about lice and lice eradication as well as counseling tips and patient material go to www.SkinPharmacies.ca/CE.

*This article was adapted from Hong CH. Treatment of Head Lice. Skin Therapy Letter – Pharmacist Edition 1(2):4-5 (2006 Sep- Oct).

• Table of Contents
• The Bottom Line – Managing Diaper Dermatitis
• Treatment of Head Lice
• Common Bacterial Skin Infections