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Pediculosis capitis

Pediculosis capitis
Literature review current through: Jan 2024.
This topic last updated: Oct 12, 2022.

INTRODUCTION — Pediculosis capitis is a common condition caused by infestation of the hair and scalp by Pediculus humanus capitis (the head louse), one of three distinct varieties of lice specifically parasitic for humans (figure 1) [1]. The clinical manifestations, diagnosis, and treatment of pediculosis capitis will be reviewed here. Other forms of louse infestation, including pediculosis corporis and pediculosis pubis, are discussed separately. (See "Pediculosis corporis" and "Pediculosis pubis and pediculosis ciliaris".)

EPIDEMIOLOGY — Pediculosis capitis occurs worldwide and in individuals of all socioeconomic backgrounds [2,3]. Children are affected most frequently.

LIFE CYCLE — The life span of the female louse is about one month, during which she lays 7 to 10 eggs per day, cementing them firmly to the base of a host hair. The eggs, commonly called "nits," are oval capsules that hatch in eight days, releasing nymphs that require another eight days to mature (picture 1A-B). After hatching, egg cases become white and more visible.

Adult head lice are gray-white, 2 to 3 mm in length (picture 2A-B), and equipped with mouth parts adapted to sucking blood and legs adapted to grasping hairs. Adults feed both on the scalp and adjacent areas of the face and neck. Adult lice can survive up to 55 hours without a host [4] but probably dehydrate and become nonviable long before their death [2].

TRANSMISSION — Direct contact with the head of an infested person is the primary mode of transmission of pediculosis capitis [5,6]. Lice do not jump, fly, or use pets as vectors.

The contribution of inanimate objects to the spread of pediculosis capitis is controversial [7,8]. While a study performed in an experimental setting suggested that use of hair dryers, combs, or towels could lead to louse transmission [9], other studies investigating the prevalence of lice on hats, bedding, and floors after exposure to an infested individual have not supported these routes as important modes of transmission [10-12].

CLINICAL MANIFESTATIONS — Pruritus occurs as an allergic reaction to lice saliva injected during feeding. In a patient without prior infestation, the onset of itching may be delayed until sensitization occurs after four to six weeks [13].

In addition to lice and nits, excoriations may be visible on the scalp, neck, and postauricular skin (picture 3). Infrequently, secondary staphylococcal infection occurs with associated cervical or nuchal lymph node enlargement.

DIAGNOSIS — Pediculosis capitis should be suspected in patients with scalp pruritus, particularly in children. Persistent pyoderma around the neck or ears should also stimulate an evaluation for pediculosis capitis.

The diagnosis is confirmed by the visualization of live lice (picture 2A, 2C). Systematically combing wet or dry hair with a fine-toothed nit comb (teeth of comb 0.2 mm apart) better detects active louse infestation than visual inspection of the hair and scalp alone [14,15]. In a comparison study, a wet-combing technique resulted in a sensitivity of 91 percent for the detection of live lice, compared with a sensitivity of 29 percent observed with visual inspection [14]. It has been suggested that wet combing is the most sensitive diagnostic technique; however, wet combing and dry combing have not been compared directly in clinical studies [14].

To perform wet combing, a lubricant such as a hair conditioner is applied to the hair prior to the following steps, which are also used for the dry-combing method [2]:

The hair is brushed or combed to remove tangles.

A fine-toothed comb is inserted near the crown until it gently touches the scalp, after which it is drawn firmly down and examined for lice after each stroke.

The entire head is combed systematically at least twice.

Nits are often more easily found than nymphs and adult lice, which are elusive (picture 1A, 1C-D). Unlike seborrheic scales, hair casts, and hair spray residue, nits are cemented securely to the hair shaft and are difficult to dislodge. Light microscopy or dermoscopy can be used to confirm a nit (picture 1B, 1E-F) [16]. Examination with a Wood's lamp causes nits to fluoresce a pale blue and can facilitate harvest for microscopic examination. (See 'Differential diagnosis' below.)

However, the finding of nits without lice does not confirm active infestation. Nits can persist after successful therapy [2]. Active infestation is suggested by the finding of many nits within one-quarter inch (6.5 mm) of the scalp; nits further from the scalp are almost always nonviable [6]. However, even this criterion results in overdiagnosis. As an example, in a study in which 1729 elementary school children were screened for lice, 28 (1.6 percent) had active lice while 63 (3.6 percent) had nits without lice, of whom 50 completed follow-up [17]. During two weeks of follow-up, only 9 of the 50 children who initially had nits alone (18 percent) converted to an active infestation. Having ≥5 nits within one-quarter inch of the scalp was associated with a higher conversion rate than fewer nits (32 versus 7 percent).

The diagnosis of lice is traumatic for some patients and parents/caregivers and can lead to concern for continued infestation even after cure is complete. Tact, reassurance, and empathy on the part of the clinician are helpful.

DIFFERENTIAL DIAGNOSIS — Nits should be distinguished from hair casts, white piedra, and black piedra:

Hair casts – Hair casts (also known as pseudonits) are white to yellow, 2 to 7 mm, keratinous, tubular sheaths that encircle hair shafts (picture 4). Hair casts may be idiopathic (primary hair casts) or may occur in association with a scalp condition such as seborrheic dermatitis or psoriasis [18,19]. Unlike nits, hair casts slide easily along the hair shaft.

Piedra – Nits also should be distinguished from white and black piedra, fungal infections most commonly found in tropical areas that present with white to beige (white piedra) or brown to black (black piedra) concretions on hair shafts (picture 5A-C) [20]. The concretions may reach up to a few millimeters in length. White piedra is caused by Trichosporon species, and black piedra is caused by Piedraia hortae. The nodules of white piedra tend to be soft and loosely adhered to the hair shaft, whereas black piedra nodules are hard and firmly attached. White piedra affects the face, axillae, and genitals more often than scalp hair. In contrast, black piedra is most likely to occur on scalp and facial hair. (See "Infections due to Trichosporon species and Blastoschizomyces capitatus (Saprochaete capitata)".)

When the diagnosis is uncertain, microscopic examination of the hair can distinguish nits from piedra and hair casts (picture 1B). Moreover, in piedra, a potassium hydroxide (KOH) preparation of an involved area will reveal fungal elements. (See "Office-based dermatologic diagnostic procedures", section on 'Potassium hydroxide preparation'.)

In addition to pediculosis capitis, scalp pruritus may occur in multiple other scalp disorders, such as seborrheic dermatitis and atopic dermatitis. The finding of nits or live lice distinguishes pediculosis capitis. (See "Cradle cap and seborrheic dermatitis in infants" and "Seborrheic dermatitis in adolescents and adults".)

TREATMENT — Treatment of pediculosis capitis is recommended. Topical pediculicides are the most common initial treatments. Manual removal of lice (wet combing) is sometimes used as an alternative to topical pediculicide therapy. Oral therapy is occasionally required for refractory infestations.

Regardless of the treatment selected, the presence of living lice should be confirmed prior to treatment [13]. Patients with nits but no detectable nymphs or adult lice likely do not have active infection if nits are only found more than 6.5 mm from the scalp. These patients do not require treatment.

Many patients with nits less than 6.5 mm from the scalp and no detectable nymphs or adult lice also do not have active infestation [17]. Clinician approaches to these patients vary. Whereas some clinicians elect to treat based upon the possibility of missing live lice during the examination, others follow patients clinically for signs of active infestation to avoid unnecessary treatment. (See 'Diagnosis' above.)

First-line treatment — Multiple topical pediculicides are accepted first-line treatments for pediculosis capitis. Wet combing is an alternative intervention that is primarily used for very young infants and patients who prefer to avoid pediculicides. (See 'Wet combing' below.)

Topical pediculicides — Examples of effective topical pediculicides include (table 1):

Pyrethroids (pyrethrins, permethrin)

Malathion

Spinosad

Topical ivermectin

Topical pediculicides should be applied according to the package instructions. Basic principles for treatment include:

Topical pediculicides should be rinsed off with water after the recommended time. Rinsing of topical pediculicides should be performed over a sink rather than in a shower or bath to limit skin exposure [13].

Rinsing with warm water is preferred over hot water to minimize vasodilation and systemic absorption [13].

Hair should not be washed with shampoo for 24 to 48 hours after treatment [13].

Topical lindane is not recommended as a first-line treatment for pediculosis capitis because of safety concerns. (See 'Lindane' below.)

Selection — Pediculicide choice should be made based on several factors, including agent-specific side effects, patient age, treatment cost, and resistance patterns to topical agents [21-29]:

Resistance – Resistance, particularly to pyrethroids and malathion, is a growing concern, and geographical variability exists in the prevalence of pediculicide resistance. A mutation in the louse kdr allele that results in decreased sensitivity of neuronal voltage-gated sodium channels has been proposed as the primary mechanism for pyrethroid resistance [30]. Rates of kdr resistance appear to be high in the United States based upon a study in which over 14,000 lice were collected from 138 collection sites in 48 states and analyzed with quantitative sequencing for kdr mutations [31]. Of the 138 collection sites, 132 (96 percent) had a mean percent resistance allele frequency of 100 percent. However, the clinical relevance of kdr mutations is brought into question by a study that found a poor correlation between mutations in kdr and treatment failure [32].

Resistance to malathion occurs via increased production of enzymes that metabolize malathion and decreased sensitivity of neuronal acetylcholinesterase to the drug [21]. Other pathways for resistance also may be involved. Resistance to malathion appears to be less prevalent in the United States than in the United Kingdom [21]. It is unclear whether this is due to the history of limited use of the drug in the United States or that the United States formulation of malathion also contains terpineol, a chemical with pediculicidal properties. In one in vitro study in Britain, fewer lice died after four hours of exposure to malathion 0.5% in isopropanol than after 30 minutes of exposure to the United States product (42 versus 96 percent) [33].

Side effects and patient ageMalathion requires longer application times than other pediculicides and is malodorous. In addition, the drug has the potential for flammability and may cause respiratory depression if ingested. The age of the child also impacts treatment selection. Safety data for use in young children vary among the pediculicides (table 1).

Drug cost – The high cost of some pediculicides may be prohibitive for some patients [34,35]. Permethrin and pyrethrins are among the least expensive topical agents [35]. United States pricing information is available in the drug information content within UpToDate.

Locations with low pyrethroid resistance — Pyrethroids (pyrethrins and permethrin) are well-tolerated and inexpensive treatments that have a long history of use for pediculosis capitis. Pyrethroids are the preferred choice for initial therapy in areas where resistance to these products has not been proven [13]. This approach is consistent with guidance issued by the American Academy of Pediatrics in 2022 [13].

Pyrethroids — Made from a natural chrysanthemum extract, pyrethrins are neurotoxic to lice [22]. Pyrethrins are often combined with piperonyl butoxide, an ingredient that inhibits pyrethrin catabolism in the louse and improves efficacy. Permethrin is a synthetic pyrethroid:

Administration – Dry hair should be saturated with the pediculicide. The pediculicide remains on the hair for 10 minutes before rinsing off with water.

A second treatment is indicated on day 9 or 10 [13]. One study of permethrin found lice-free rates of 83 percent on day 2, decreasing to 46 percent on day 8 before a second treatment, and then increasing to 78 percent on day 9 after the second treatment and remaining at 78 percent on day 15 [36].

In the United Sates, lotions containing pyrethrins and piperonyl butoxide are available without a prescription, as is a 1% concentration of permethrin. Permethrin 5% is not more effective than the over-the-counter permethrin 1% preparation [37].

Precautions Pyrethroids are generally well tolerated. However, pyrethrins may cause breathing difficulties in patients with ragweed allergy, and permethrin use is not recommended in patients who are allergic to chrysanthemums. Skin irritation is a potential side effect.

Pyrethrins can be used for patients ≥2 years of age. Permethrin can be used for patients ≥2 months of age.

Locations with prevalent pyrethroid resistance — In areas where resistance to pyrethroids has been documented, or in patients who have failed to respond to appropriately administered treatment with a pyrethroid, other pediculicides (such as malathion, spinosad, and topical ivermectin) are appropriate treatments. In the United States, all of these products are available only by prescription.

Malathion — Malathion is an organophosphate cholinesterase inhibitor that exerts neurotoxic effects on lice. The agent has both pediculicidal and ovicidal properties. In comparison with pyrethroids, malathion is more expensive, has an additional side effect of flammability, and requires a longer time of application.

In the United States, malathion is available as a product that includes terpineol, an ingredient with additional pediculicidal properties (see 'Selection' above). One in vitro study found that malathion 0.5% with terpineol was most effective at killing head lice, compared with pyrethroids and lindane [23]:

Administration Malathion lotion is applied to dry hair and the scalp and left in place for 8 to 12 hours before washing off with a nonmedicated shampoo [38]. The hair should be left uncovered, and heat sources should not be used to dry the hair. A single application of malathion is sufficient for most patients. If live lice are visualized seven to nine days after treatment, a second treatment is indicated.

Some studies have suggested that shorter application times may also be effective [39,40]. In one small, investigator-blinded, randomized trial, lice were eradicated in 98 percent of patients treated with one or two 20-minute applications of malathion with terpineol [41].

Precautions Malathion is malodorous, and its vapor is irritating to the eyes. The potential flammability of the product due to high alcohol content has also been a concern. There is a theoretical risk for respiratory depression from accidental ingestion.

Malathion is contraindicated in children under the age of two, and studies of the safety of malathion in children under the age of six are limited. One randomized trial involving topical malathion therapy found no evidence of systemic acetylcholinesterase inhibition in children as young as two years of age [42].

Spinosad — Spinosad is a fermentation product of the soil bacterium Saccharopolyspora spinosa. This drug compromises the central nervous system of lice by interfering with the nicotinic acetylcholine receptor, resulting in neuronal excitation and paralysis [43].

Two manufacturer-sponsored phase III, multicenter, randomized trials compared the efficacy and safety of spinosad 0.9% cream rinse with permethrin 1% cream rinse plus nit combing [44]. Patients who had residual live lice seven days after an initial treatment were instructed to repeat application of the same therapy. After treatment, approximately 85 percent of spinosad-treated subjects were lice-free, compared with approximately 44 percent of those treated with permethrin. Individuals treated with spinosad were also less likely to require a second application:

Administration Spinosad is supplied as a 0.9% topical suspension. Therapy involves application to completely cover the scalp and hair. The hair should be dry prior to treatment. After application, spinosad should be left on for 10 minutes. Subsequently, the scalp and hair should be thoroughly rinsed with warm water to completely remove the product. Shampooing of the hair can be performed at any time after treatment. Treatment should be repeated if live lice remain seven days after the initial application.

Precautions – Skin irritation is a potential side effect of spinosad therapy. Spinosad is not recommended for use in children under six months of age.

Topical ivermectin — Topical ivermectin functions by binding to glutamate-gated chloride channels in lice, thereby inducing paralysis and death [35].

Topical ivermectin therapy is supported by two randomized trials that found that a single 10-minute application was superior to a placebo lotion for the eradication of lice [45]. The primary efficacy endpoint in both trials was the number of index patients (youngest household member with at least three live lice detected on examination) who were louse-free at days 2, 8, and 15. A combined analysis of the trial results revealed that among the index patients, 131 of 138 (95 percent) treated with topical ivermectin 0.5% lotion and 46 of 147 (31 percent) treated with the placebo lotion were free of live lice on day 2. By day 15, live lice were absent in 74 and 18 percent of patients, respectively. In addition, patients in the topical ivermectin group were more likely to be free of pruritus on day 2; 67 versus 43 percent denied pruritus. Adverse events were infrequent and occurred at similar rates in both groups:

Administration – Topical ivermectin 0.5% lotion is administered via a single application to dry hair. As with malathion, a single application is sufficient. The lotion is applied to thoroughly coat the hair and scalp and is rinsed off with water after 10 minutes.

Precautions – Topical ivermectin generally is well tolerated. Potential adverse effects include ocular irritation, dry scalp, and a burning sensation on the skin [35,45]. The safety of ivermectin in infants under the age of six months is not established.

In 2020, the US Food and Drug Administration (FDA) approved ivermectin 0.5% lotion for nonprescription use; however, commercial availability is limited [46].

Wet combing — Mechanical removal of lice by wet combing is an alternative treatment for patients who are too young for pediculicide treatment or who desire to avoid pediculicide therapy. The time and care required to perform wet combing and the need for multiple sessions are deterrents for some patients.

The relative effectiveness of wet combing and medical therapy is uncertain. In one study in the United Kingdom, wet combing was only half as effective as treatment with malathion (cure in 38 versus 78 percent, respectively) [47]. Another United Kingdom study found that wet combing was much more effective than a single treatment with either malathion or permethrin (cure in 57 versus 13 percent) [48]. However, there were significant methodologic issues with this latter study, including unblinded allocation of patients, the use of an inadequate regimen of pediculicide, and different lengths of follow-up in the two arms of the study [49]:

Administration – Combing is performed with a fine-toothed comb; the hair should be wet, with an added lubricant such as hair conditioner [50]. The combing technique is the same as the combing procedure used for the diagnosis of louse infestation. (See 'Diagnosis' above.)

Combing is done until no lice are found in each session, with repeat sessions every three to four days for several weeks, continuing for two weeks after any session in which a large, adult louse is found [2]. The procedure may take 15 to 60 minutes depending on the thickness/length of hair.

Refractory infestations — The most common causes of treatment failure are lack of adherence to treatment, improper application of treatment, and continued contact with other infested individuals. Resistance to specific topical treatments is a problem in some locations. (See 'Selection' above.)

If a patient fails to respond to an appropriate course of treatment with a topical pediculicide and reinfestation does not appear to be a factor, switching to an alternative topical pediculicide that has not been associated with local resistance is the typical next step. Oral ivermectin is a treatment option for patients who fail topical therapy [51,52].

Oral ivermectin — Ivermectin interferes with neurotransmission in arthropods and helminths, leading to paralysis and death:

Administration – Dose regimens used for pediculosis capitis have included a single 200 or 400 mcg/kg dose, usually repeated after 7 to 10 days or repeated at this point if live lice remain visible [51-57]. Because it is not clear that a 400 mcg/kg dose is superior, our preferred approach is a single 200 mcg/kg dose repeated after one week:

In a randomized trial of 80 children with pediculosis capitis, treatment with ivermectin (200 mcg/kg) was compared with malathion 0.5% lotion [53]. Patients were given a single treatment of ivermectin or malathion, which was followed by a second treatment on day 8 if live lice were detected. Ivermectin and malathion were similarly effective; by day 15, 92.5 and 95 percent of patients, respectively, were cured.

In a randomized, double-blind trial (n = 812), patients who failed home therapy with a pyrethroid or malathion were treated with either malathion 0.5% lotion applied by study staff or oral ivermectin (400 mcg/kg) [51]. Participants in both groups were given two treatments separated by one week. Ivermectin therapy was associated with a significantly higher rate of eradication of head lice; 95 versus 85 percent of subjects were cured of infestation. The incidence of adverse effects was similar in both groups.

Precautions Ivermectin generally is well tolerated when used for pediculosis capitis; most serious adverse effects have occurred during treatment for severe microfilarial infections [58,59]. Ivermectin is not recommended for pregnant women or children weighing less than 15 kg, since safety has not been established in these populations. (See "Anthelminthic therapies", section on 'Ivermectin'.)

Other therapies — A variety of other therapies have been reported as effective for pediculosis capitis, such as dimethicone, lindane, trimethoprim-sulfamethoxazole, 1,2-octanediol, a synthetic detergent cleanser, and a variety of physical methods. Routine use of many of these interventions is precluded by limited efficacy data or safety concerns.

Oily home products (eg, olive oil, butter, petroleum jelly) are sometimes used in the hopes of suffocating lice. However, lice are difficult to suffocate, and a small study of such products concluded that they are not effective [40]. Gasoline and kerosene are highly flammable and should not be used for pediculosis capitis [13].

Dimethicone — Topical dimethicone (also known as dimethicone) is widely used for pediculosis capitis in Europe. Dimethicone is a nonpesticide, silicone-based material believed to work by coating lice and disrupting their ability to manage water.

Efficacy of dimethicone is documented in multiple studies [60-64]. In a randomized, open-label trial in the United Kingdom (n = 90), a single 15-minute application of dimethicone 4% gel was superior to two 10-minute applications of permethrin 1% cream rinse (70 versus 15 percent treatment success rate) [61]. A separate assessor-blinded United Kingdom trial (n = 73) that compared two eight-hour or overnight applications of dimethicone 4% lotion with two 12-hour or overnight applications of malathion 0.5% liquid also found dimethicone more effective [62]. A Brazilian observer-blinded randomized trial (n = 145) found two eight-hour applications of a product with 92% dimethicone superior to two 30-minute applications of a permethrin 1% lotion [63].

A disadvantage of many dimethicone pediculicides is flammability [65].

Lindane — Lindane shampoo is not recommended for the treatment for pediculosis capitis because it has been associated with rare neurologic adverse effects and widespread resistance [13,23].

Lindane toxicity — Lindane is an organochlorine insecticide that inhibits neurotransmission in parasitic arthropods. Neurologic toxicity resulting in seizures and death has been reported in humans following topical lindane therapy [66]. Most of these events have occurred after prolonged or repeated application of lindane but, in rare cases, have followed a single application [66].

Although the drug has been banned in some countries and the state of California [67] and the American Academy of Pediatrics no longer recommends use of this therapy [13], lindane shampoo remains available by prescription elsewhere in the United States. The US FDA has placed a black box warning on the drug labels, cautioning that lindane shampoo should only be used as a second-line treatment in patients who cannot tolerate or have failed other therapies for the treatment of scabies or lice. Lindane is contraindicated in patients with skin disorders that may lead to increased systemic absorption (eg, atopic dermatitis, psoriasis).

If used, lindane should be given only as single application; retreatment should be avoided. Other measures to minimize toxicity include:

Prescribe 1 ounce of lindane shampoo to treat an average adult; no more than 2 ounces should be prescribed.

Lindane shampoo prescribed for pediculosis capitis should be washed off after four minutes.

Caregivers applying the drug to patients should wear gloves that are less permeable to lindane (nitrile, latex, neoprene, or sheer vinyl). Natural latex gloves should not be used. Caregivers should thoroughly wash their hands after application.

Trimethoprim-sulfamethoxazole — Combination therapy with topical permethrin and oral trimethoprim-sulfamethoxazole may be more effective than treatment with permethrin alone. The mechanism of action of trimethoprim-sulfamethoxazole may involve the death of symbiotic bacteria in the louse gut that produce B vitamins necessary for louse survival [68].

The combination of topical permethrin (1%, applied for ten minutes with a repeat application after one week if necessary) plus oral trimethoprim-sulfamethoxazole (10 mg/kg per day trimethoprim in two divided doses for ten days) was compared with either drug alone in a randomized trial of 115 children [68]. Compared with topical permethrin alone, dual therapy was associated with a higher rate of success at four weeks (93 versus 72 percent). Trimethoprim-sulfamethoxazole alone yielded a success rate of 78 percent. Although rare, potential adverse effects of trimethoprim-sulfamethoxazole include Stevens-Johnson syndrome, neutropenia, hemolysis, and renal impairment. The authors of the study concluded that dual therapy should be reserved for resistant cases.

1,2-octanediol — Data from randomized trials suggest that topical preparations containing 1,2-octanediol, an agent that may disrupt cuticular lipids on head lice and their eggs, are beneficial for the treatment and prevention of pediculosis capitis [69,70]. Topical 1,2-octanediol is not commercially available in the United States.

Synthetic detergent cleanser — Two prospective studies of a synthetic detergent cleanser applied to the head and then dried, with a goal of suffocating lice, reported a 96 percent cure rate [71,72]. The studies had significant flaws, including lack of a control group, lack of blinding, and potentially inappropriate diagnostic criteria [73]. Further studies are needed before this approach can be recommended.

Physical methods

Hair removal Shaving hair is anecdotally reported as a method of eradicating head louse infestation [74]. However, studies evaluating this method of treatment have not been performed, and the procedure may be psychologically distressing for some patients.

Electric comb – A comb that uses an electric current generated by an AA battery to electrocute lice is marketed for the treatment of head lice. Although there are anecdotal reports of successful treatment with the device [75], there are no published clinical trials.

Heated air – An unblinded study reported louse eradication with high-volume heated air blown at the scalp for 30 minutes [76]. Few patients overall received the high-volume heated air treatments, and patients younger than age six were excluded. While awaiting the results of larger controlled trials that compare methods of delivering heat and assess cure, safety, training, and costs, such treatment cannot be recommended.

RETURN TO SCHOOL — Children should not be excluded from school based upon the presence of live lice or nits [77]. Lice often are present for weeks prior to detection. Furthermore, the majority of children with nits do not develop active infestation [17]. Affected children should avoid direct head contact with other individuals and should be treated promptly with a topical pediculicide or wet-combing session. The Centers for Disease Control provides a brief summary of the recommended approach to children with lice in schools.

Control of outbreaks in schools may be facilitated by examination of teachers and pupils who may have had close head-to-head contact with an affected child and by assigning students individual wall hooks or lockers for storing caps and coats [39]. Education programs designed to increase knowledge about pediculosis capitis and methods to prevent infestation in a community may also be beneficial [78].

HOUSEHOLD RECOMMENDATIONS — Household members should be examined and treated if infested (live lice or nits within 1 cm of the scalp detected); bedmates should be treated prophylactically [13].

Louse survival off the scalp beyond 48 hours is unlikely [13]. It is reasonable to recommend washing hair care items, clothing, and linen used by the infested person during the two days prior to therapy in hot water and drying the items on a high-heat dryer cycle [13]. Temperatures should reach at least 130°F. Items that cannot be washed may be dry-cleaned or stored in a sealed plastic bag for two weeks [1,13]. Vacuuming of furniture and carpeting on which the infested person sat or lay down has also been suggested; of note, the risk of transmission from these sites is low [6,13]. Spraying the home with a pediculicide is not recommended.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pediculosis".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

Basics topics (see "Patient education: Lice (The Basics)")

Beyond the Basics topics (see "Patient education: Head lice (Beyond the Basics)" and "Patient education: Pubic lice (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

Overview Pediculosis capitis (head lice) is a scalp infestation that most frequently occurs in children. Affected individuals may be asymptomatic or may complain of scalp or neck pruritus. (See 'Clinical manifestations' above.)

Diagnosis Pediculosis capitis is diagnosed by visual examination. In cases of active infestation, louse eggs (nits) are found on hair shafts, and crawling nymphs and adult lice are present. Wet combing is a useful technique for locating adult lice or nymphs. The presence of nits alone does not confirm active infestation. (See 'Diagnosis' above.)

Treatment Several topical pediculicides are available for the treatment of pediculosis capitis:

Selection Resistance to topical agents that kill lice via neurotoxic mechanisms has been increasingly reported and varies geographically. The selection of a topical agent should be based upon local resistance patterns and consideration of adverse effects and patient age. Treatment with lindane is not recommended due to the potential for neurologic side effects and the drug's relatively low efficacy. (See 'Topical pediculicides' above.)

Preferred first-line treatments First-line treatment options for pediculosis capitis include pyrethroids, malathion, spinosad, and topical ivermectin (table 1). The safety, low cost, and easy availability of pyrethroids have led to the widespread use of these drugs as initial agents. In areas in which pyrethroid resistance is not likely, we suggest use of a pyrethroid as first-line therapy (Grade 2A). (See 'Topical pediculicides' above.)

Treatment failure Treatment failure may occur secondary to lack of adherence to the treatment regimen or reinfestation. Clinicians should consider these factors, in addition to the possibility of resistance, when evaluating patients with an apparent lack of response to therapy. (See 'Refractory infestations' above.)

School attendance and management of close contacts Children with pediculosis capitis do not need to be excluded from school. Household members and close contacts should be examined for infestation. Individuals who share bedding with the affected person should be treated prophylactically. (See 'Return to school' above and 'Household recommendations' above.)

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Topic 4035 Version 33.0

References

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