Lice Organism-Specific Therapy 

Updated: Jun 12, 2020
  • Author: Darvin Scott Smith, MD, MSc, DTM&H; Chief Editor: Michael Stuart Bronze, MD  more...
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Therapeutic Regimens for Head, Body, and Pubic Lice

Three main types of lice that infest humans include head lice (Pediculus humanus capitis), body lice (Pediculus humanus corporis), and pubic lice (Phthirus pubis). The general signs and symptoms of lice include intense pruritus, general restlessness, and red bumps on the skin in the case of body lice. To diagnose a lice infestation, direct observation of lice and/or nits and wet-combing of the hair to reveal organisms are useful techniques. [1, 2]

Treatment recommendations for lice, as well as special considerations, are listed below.

Head lice (P humanus capitis)  [1, 3, 4]

Permethrin 1% lotion is administered as follows:

  • Apply to hair after washing with shampoo; use a sufficient amount to saturate the hair and scalp; leave on hair for no longer than 10 minutes, and then rinse with water and towel dry; apply a second treatment 7 days after first application; remove any remaining nits with the nit comb provided
  • Inexpensive, well-tolerated

Malathion 0.5% lotion is administered as follows:

  • Apply lotion on dry hair in an amount just sufficient to thoroughly wet the hair and scalp; wash hands after applying to scalp; allow hair to dry naturally; do not use an electric heat source, and allow hair to remain uncovered; after 8-12 hours, shampoo hair; rinse, and use a fine-toothed (nit) comb to remove dead lice and eggs; repeat with a second application of malathion 7-9 days later

Benzyl alcohol 5% lotion is administered as follows:

  • Apply lotion to saturate the hair and scalp, especially behind the ears and on the back of the neck; leave lotion on hair for 10 minutes, and rinse with water; repeat treatment after 7 days

Spinosad is administered as follows:

  • Apply to dry scalp and hair using only the amount needed to cover the scalp and hair; rinse off with warm water after 10 minutes; repeat treatment recommended 7 days after first treatment, especially if live lice are seen

Pyrethrin and piperonyl butoxide is administered as follows:

  • Avoid in patients with allergy to chrysanthemum or ragweed; various over-the-counter products exist
  • Apply to dry hair; after 10 minutes, massage with water to foam, then rinse; repeat in 7-10 days

Ivermectin 0.5% lotion is administered as follows:

  • Apply to dry hair and scalp; rinse 10 minutes after application
  • Single application only

Body lice (P humanus corporis)

Body lice can generally be treated by hygiene alone. [1, 5]

Weekly clothing changes and heat-based laundering of clothing (52°C [125.6°F] minimum for 30 min) and bedding are recommended.

For cases of body lice found on body hairs, topical pediculicides are effective, including permethrin 5% cream, with an application period of 8-10 hours all over the body.

Low-potency topical corticosteroid cream can be applied to irritated areas twice daily for several days after elimination of lice in order to provide symptomatic relief.

Pubic lice (P pubis), also known as “crabs”

P pubis is commonly transmitted by sexual contact. Patients with P pubis infestation present to healthcare providers because they experience pruritus or because they notice the lice or nits in their pubic hair. [1, 6]

Permethrin 1% cream is administered as follows:

  • Ensure skin is dry and cool before applying to all affected areas or suspect areas; wash off after 10 minutes; remove nits with tweezers or by hand; repeated treatment may be needed if lice are still observed 7-10 days later

Pyrethrin and piperonyl butoxide (mousse or shampoo) is administered as follows:

  • Avoid in patients with allergies to chrysanthemum or ragweed
  • Ensure skin is dry and cool before applying to all affected areas or suspect areas; wash off after 10 minutes; remove nits with tweezers or by hand; repeated treatment may be needed if lice are still observed 7-10 days later

Malathion 0.5% lotion is administered as follows:

  • Apply the lotion for 8-12 hours, and wash off; 1 treatment generally is sufficient

Topical ivermectin is administered as follows:

  • Apply 0.5% lotion to dry hair in amount sufficient (up to one 4-oz tube) to thoroughly coat the hair; leave lotion on for 10 minutes, and then rinse with water; for single use only (do not retreat)

Special considerations  [2, 3, 4, 5]

It is important to ensure that individuals with body and/or pubic lice wash their clothes, towels, and bedding with hot water and dry them using the hot setting on the dryer; dry cleaning or sealing clothes in plastic bags for 2 weeks is also acceptable.

Head lice resistance to permethrin is rising rapidly; in resistant cases, consider a greater concentration of permethrin or longer treatment exposure before attempting alternate therapies.

Sexual partners of those with pubic lice should likewise be treated, and sexual contact should be avoided until the lice infestation is successfully cured. Nonsexual contacts need not be treated.