eMedicine Specialties > Infectious Diseases > Skin and Soft-Tissue Infections
Pediculosis: Treatment & Medication
Updated: May 5, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Treatment
Medical Care
P humanus corporis
- Treatment of P humanus corporis infestation with any pediculicide is usually unnecessary because the louse lives on the clothing.
- Treatment of clothing and bed linens includes washing them in hot water and drying them with high heat. Dry cleaning is also effective for killing lice and their nits on clothing.
- Education about hygiene and accessibility to laundering facilities are important in preventing the spread of body lice and reinfestation.8
- In cases of heavy pediculosis, treatment of the body with a pediculicide shampoo or lotion may be beneficial, especially if the patient also has confirmed or suspected concomitant head or pubic louse infestation. Oral ivermectin 12 mg given as 3 doses 7 days apart has also been shown to be efficacious in a cohort of homeless men.9
P humanus capitis and P pubis
- Pediculicides: These include permethrin, lindane, malathion, or mercuric oxide ointment.
- The pyrethroids are neurotoxic to lice; however, they are not very effective against developing nits, although they do have a residual effect. Lotions appear to be more efficacious than shampoos because of their increased contact time with the skin and hair of affected areas. Permethrin is available as a 1% solution (Nix) and as a 5% solution (Elimite), and a formulation of pyrethrin and piperonyl butoxide (Rid) is available. A-200 shampoo also contains benzyl alcohol. Permethrins are usually the first line of treatment, although resistance to permethrin is an increasingly important problem.
- Lindane (hexachlorocyclohexane, a chlorinated hydrocarbon) is in the same pharmacologic class as dichlorodiphenyl trichloroethane (DDT). The use of lindane is controversial because of its known CNS toxicity.10 The compound is extremely lipid-soluble and is therefore highly permeable to the CNS. Acute lindane poisoning has been reported after ingestion of amounts as small as 5 mL or 50 mg. Kwell (lindane shampoo) has been removed from the Canadian market because of the availability of safer alternatives.
- Malathion (Ovide) is an irreversible acetylcholinesterase inhibitor that is specific for insects. The US Food and Drug Administration (FDA) recently approved malathion for use against head lice in the United States. Malathion is available as a 0.5% and a 1% solution.
- A study in children showed that treatment with Chick-Chack, a natural remedy that contains coconut oil, anise oil, and ylang ylang oil, had greater than 90% efficacy.11
- Mercuric oxide ointment is useful in the treatment of eyelash infestation with P pubis.
- Resistance to over-the-counter pediculicides (eg, permethrin, pyrethrin) is common, leading some parents to use toxic prescription medications containing lindane and malathion.
- Benzyl alcohol lotion 5% was recently approved by the FDA for P capitis infestation. Although benzyl alcohol lotion needs to be applied twice, it might be an easier and safer alternative to lindane and malathion. With all treatments used to eliminate live lice, careful combing and removal of all nits from the hair, as well as cleaning of other articles (ie, hair accessories, towels, bedding, clothing), are essential steps to prevent reinfestation.
- The safety and effectiveness of benzyl alcohol lotion 5% was demonstrated in 2 multicenter, randomized, double-blind studies of 628 patients aged 6 months and older with active head lice infestation. The participants received two 10-minute treatments of either benzyl alcohol lotion or topical placebo, 1 week apart. When observed 2 weeks following the final treatment, more than 75% of those treated with benzyl alcohol lotion were lice-free, whereas 4.8%-26.2% who received the placebo vehicle were lice-free.12
- Asphyxiants: Petrolatum (twice daily for 7-10 days) is often used, with good results, for eyelash infestation. The petrolatum covers the lice and their nits, preventing respiration. The dead lice are removed mechanically, usually with tweezers.
- Specific oral antibiotics: Oral antihelminthics, including ivermectin, levamisole, and albendazole,13 have been found to be effective against head louse infestation. Administration should be repeated in 7-10 days to kill lice emerging from nits that may have survived the first treatment. Co-trimoxazole (ie, trimethoprim and sulfamethoxazole) was initially reported to be efficacious; however, controlled studies have shown only minimal eradication.
- Mechanical removal and shaving
- Solvents are available to help dissolve the cement away from the nit and to aid in mechanical removal of nits with fine-tooth combs (eg, LiceMeister). Formic acid and plain white vinegar have been shown to be effective solvents.
- Most studies have shown that mechanical removal alone (ie, wet-combing every 2-3 d for a minimum of 2 wk) is not as effective as when this technique is combined with a pediculicide.14
- Shaving is effective but is usually not necessary or socially acceptable. However, in resistant disease, it may be a consideration.
Medication
The goals of pharmacotherapy are to eradicate the infestation, to prevent complications, and to reduce morbidity.
Pediculicides
In cases of heavy pediculosis, treatment of the body with a pediculicide shampoo or lotion may be beneficial, especially if the patient also has confirmed or suspected concomitant head or pubic louse infestation.
Permethrin (Nix, Acticin, Elimite)
Usually the first line of treatment in head, pubic, and severe body louse infestation. Available as a lotion and shampoo.
Adult
Wash hair with nonmedicated shampoo and towel dry; apply 1% lotion to affected areas; leave on hair for 10 min before rinsing; second application may be used in 7 d prn
Pediatric
Apply as in adults
None reported
Documented hypersensitivity
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Adverse effects include pruritus, burning, stinging, numbness, erythema, and edema of the scalp; discontinue use upon irritation or hypersensitivity
Pyrethrins (RID Mousse, RID Shampoo, R&C, A200)
Treatment of P humanus infestations. Stimulates nervous system of parasite, causing seizures and death. First-line treatment in head, pubic, and severe body louse infestation.
Adult
Apply shampoo to dry hair and allow to set for 10 min before rinsing; repeat in 1 wk prn
Pediatric
Apply as in adults
None reported
Documented hypersensitivity
Pregnancy
X - Contraindicated; benefit does not outweigh risk
Precautions
Do not apply to eyes, face, or mucous membranes; discontinue use if irritation occurs
Ivermectin (Mectizan)
Binds selectively with glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing cell death. Half-life is 16 h; metabolized in liver. DOC for onchocerciasis and strongyloidiasis. Recently shown to be effective against pediculosis but not yet approved by FDA. Not effective against nits.
Adult
12 mg PO as single dose; may repeat in 1 wk prn
Pediatric
<5 years: Not recommended
>5 years: 0.2 mg/kg PO as single dose
May interact with other ligand-gated chloride channels, such as those gated by GABA; should not be used with drugs that have similar effects (eg, benzodiazepines, barbiturates, valproic acid)
Documented hypersensitivity; meningitis
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Adverse effects include nausea, vomiting, and, uncommonly, ophthalmologic reactions (eg, corneal opacity, uveitis, conjunctivitis, optic neuritis)
Lindane (Kwell, Scabene)
Stimulates nervous system of parasite, causing seizures and death. Chlorinated insecticide available as 1% lotion, cream, and shampoo. Second-line treatment if other agents fail or are not tolerated. Not very safe in children because of transcutaneous absorption that leads to neurotoxicity. Overall, permethrin is a safer choice.
Adult
Shampoo: Apply to dry head or pubic hair and surrounding areas; allow to set for 4 min, then lather for 4 min and rinse; repeat in 7 d prn
Lotion: Apply to affected skin/hair; put on clean clothing; rinse off in 8-12 h
Pediatric
Infants and children: Apply thin film topically over entire body, including hairline, neck, scalp, temple, and forehead; leave on 6-8 h before washing off with water; may repeat in 1 wk if necessary; not to exceed 30 g/application
Oil-based hairdressings may increase toxicity of lindane
Documented hypersensitivity; neonates; acutely swollen skin or Norwegian scabies
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Caution if history of seizures; do not apply to eyes, face, or mucous membranes; caution in pregnancy; adverse reactions have been reported (eg, DIC, aplastic anemia)
Malathion (Ovide)
Recently approved (1999) by US FDA to treat head lice. Irreversible cholinesterase inhibitor that is hydrolyzed and therefore detoxified rapidly by mammals but not by insects; ovicidal and pediculicidal. Binds to hair and provides some residual protection after therapy. Available as 0.5% and 1% aqueous-based lotions.
Adult
Apply lotion to dry hair; leave on 8-12 h, rinse; repeat in 7 d prn
Pediatric
<2 years: Not recommended
>2 years: Apply as in adults
None reported; however, potential for interaction with aminoglycosides and antimyasthenics
Documented hypersensitivity
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Contains flammable alcohol; do not expose lotion or wet hair to open flame or electric heat (eg, hair dryers); allow hair to dry naturally and uncovered following application; avoid contact with eyes; flush eyes immediately with water if contact occurs
Mercuric oxide
Ointment (1%) is treatment of choice for Phthirus palpebrarum. For louse infestation of eyelashes, inspect eyelids and remove nits mechanically.
Adult
Apply to eyelashes qid for 14 d
Pediatric
Apply as in adults
Not to be used with topical sulfur or iodine compounds
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Avoid direct contact with eyes; adverse effects include sensitization, contact dermatitis, and mercury poisoning (eg, nausea, headache, dizziness, gingivitis); discontinue use if persistent erythema, pain, or edema occurs
Isopropyl myristate (Resultz)
Not available in the United States (currently in phase III clinical trials). Available in Canada and Europe. Noninsecticide-based drug containing isopropyl myristate, an ingredient commonly used in cosmetics. Mode of action is a mechanical process that weakens the waxy shell of lice, resulting in internal fluid loss and dehydration.
Adult
Apply to dry hair and massage into hair until the scalp and back and sides of neck are thoroughly wet; leave on for 10 min, then rinse with warm water; repeat in 7 days to kill any eggs that might have hatched
Protect eyes with towel or washcloth during application
Pediatric
<4 years: Not established
>4 years: Administer as in adults
None reported
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
For external use only; do not use near eyes; if contact with eyes, immediately flush with water; soak all combs and brushes in hot water for 10 min; carefully inspect family members daily between treatments and for at least 2 wk after treatment; stop use if skin irritation or infection occurs, or infestation of eyebrows or eye lashes occurs
Benzyl alcohol lotion
Benzyl alcohol inhibits lice from closing their respiratory spiracles, allowing the lotion to obstruct the spiracles, which ultimately results in asphyxiation. Does not elicit ovicidal activity. Contains 5% benzyl alcohol.
Adult
Apply lotion to dry hair, using enough to completely saturate scalp and hair; rinse off with water after 10 min; repeat treatment in 1 wk
Pediatric
<6 months: Do not use
>6 months: Apply as in adults
None reported
Documented hypersensitivity
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
May cause irritation to skin, scalp, and eyes (avoid eye exposure and flush immediately with water if contact occurs); application site anesthesia and hypoesthesia may occur; serious adverse events (eg, respiratory distress, seizure, coma) and death with benzyl alcohol have been well documented in premature infants; IV administration of products containing benzyl alcohol has been associated with neonatal gasping syndrome consisting of severe metabolic acidosis, gasping respirations, progressive hypotension, seizures, CNS depression, intraventricular hemorrhage, and death in preterm, low birth weight infants; neonates (ie, <1 mo or preterm infants with a corrected age <44 wk) could be at risk for gasping syndrome if treated
Anti-infectives
Therapy must be comprehensive and cover all likely pathogens in the context of this clinical setting.
Trimethoprim and sulfamethoxazole (Septra, Bactrim DS)
Normally used to treat Pneumocystis carinii infection, acne, and toxoplasmosis. Commonly used as prophylaxis against UTIs. Shown to be effective as a pediculicide.
Adult
7-10 mg/kg TMP PO for 7 d
Pediatric
<6 months: Not recommended
>6 months: Administer as in adults
May increase PT when used with warfarin (perform coagulation tests and adjust dose accordingly); coadministration with dapsone may increase blood levels of both drugs; coadministration of diuretics increases incidence of thrombocytopenia purpura in elderly people; phenytoin levels may increase with coadministration; may potentiate effects of methotrexate in bone marrow depression; hypoglycemic response to sulfonylureas may increase with coadministration; may increase levels of zidovudine
Documented hypersensitivity; megaloblastic anemia due to folate deficiency
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Discontinue at first appearance of skin rash or any sign of adverse reaction; obtain CBC counts frequently; discontinue therapy if significant hematologic changes occur; goiter, diuresis, and hypoglycemia may occur with sulfonamides; prolonged IV infusions or high doses may cause bone marrow depression (if signs occur, give 5-15 mg/d leucovorin); caution in folate deficiency (eg, persons with chronic alcoholism, elderly people, those receiving anticonvulsant therapy, those with malabsorption syndrome); hemolysis may occur in individuals with G-6-PD deficiency; patients with AIDS may not tolerate or respond to TMP-SMZ; caution in renal or hepatic impairment (perform urinalyses and renal function tests during therapy); administer fluids to prevent crystalluria and stone formation
Fluorescein dye strips (SoftGlo strips)
Used with white petrolatum. This is an off-label use of dye strips used in the diagnosis of corneal abrasion.
Adult
Apply to eyelashes nightly for 3 nights
Pediatric
Apply as in adults
None reported
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Vision may become blurred with use of white petrolatum
More on Pediculosis |
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| Differential Diagnoses & Workup: Pediculosis |
 Treatment & Medication: Pediculosis |
| Follow-up: Pediculosis |
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Further Reading
Keywords
pediculosis, lice, crabs, louse infestation, lice infestation, ectoparasites, pubic lice, pubic louse, head lice, head louse, body lice, body louse, Pediculus humanus capitis, P humanus capitis, Pediculus humanus corporis, P humanus corporis, Phthirus pubis, P pubis, Pediculus humanus humanus, P humanus humanus, human pests, Anoplura, sucking lice, insect infestation, insect bite, nit, vector-borne disease, typhus, relapsing fever, trench fever, plica polonica, vagabond disease, vagabond skin, pediculicide, permethrin, lindane, malathion, mercuric oxide ointment, pyrethrin, piperonyl butoxide, hexachlorocyclohexane
