Head Lice: Diagnosis and Therapy

Gabriel J. Martinez-Diaz, MD; Anthony J. Mancini, MD


Dermatology Nursing 

In This Article


Treatment for head lice is recommended for individuals diagnosed with an active infestation, and prophylactic therapy is recommended for bedmates and immediate members of the household of the infested index patient (AAP, 2009). All close contacts should be examined, and those with evidence of an active infestation should also be treated. Treatment of all contacts of the infested patient who require therapy should be done concurrently, so as to minimize the transmission cycle (Centers for Disease Control and Prevention [CDC], 2008; Diamantis et al., 2009; Namazi, 2003).

Table 2 lists the most commonly utilized therapies for head lice infestation. Several of these are discussed briefly below. Environmental decontamination, an important adjunct to treatment as well as prevention, is discussed in the Patient Education section.

Over-the-counter Medications

Pyrethrins, naturally derived from chrysanthemum extract, cause neurotoxicity and eventual paralysis of head lice by interfering with sodium transport (Ko & Elston, 2004). The addition of pyrethrins to piperonyl butoxide provides synergism, as the latter interferes with metabolism of the former, thereby extending its half-life (Lebwohl, Clark, & Levitt, 2007). This class includes such agents as Pronto®, Rid®, and A200®, among others. Treatment failures may be seen and depend on the local lice resistance patterns.

Prescription Medications

Since 1995, lindane has been designated as a "second-line" treatment, meaning it should be used only when other first-line treatments for lice have failed (Thomas et al., 2006). The efficacy of lindane, an organochloride compound, has decreased in recent years because of increasing lice resistance. Lindane is generally not as effective as other treatments and there have been concerns about its safety (West, 2004; Zargari et al., 2006). Overuse, misuse, or accidental ingestion of lindane can result in toxicity to the brain and other parts of the nervous system; for this reason, it is recommended this agent be considered only in patients who have failed treatment with, or cannot tolerate other pediculicidal medications that pose less risk. The CDC recommends against the use of lindane in premature infants, pregnant or breast-feeding women, individuals with a history of seizures or irritated skin/sores on the scalp, and infants, children, the elderly, or persons who weigh less than 110 pounds (CDC, 2008). Lindane use has been banned in the state of California since 2002 (Humphreys et al., 2008). Malathion is an organophosphate (acetylcholinesterase inhibitor) that works by causing respiratory paralysis in the louse (Elston, 2005). Malathion 5% lotion (Ovide®) kills live lice and their eggs, and is approved for use in children 6 years of age and older. Treatment with malathion has a favorable efficacy profile, given low observed resistance, and is highly effective. In the United States, lice have become increasingly resistant to pyrethroids and lindane, but not to malathion (Meinking et al., 2004). Resistance to malathion has been reported in the United Kingdom, however (Silverton, 1972).

Benzyl alcohol 5% lotion (Ulesfia™) is a new addition to the prescription lice therapy market in the United States. This product is the first FDA-approved, non-neurotoxic prescription product for treating head lice, and works via physical blockage of the respiratory mechanism of head lice. Although head lice have evolved the ability to close their breathing spiracles upon exposure to potentially suffocating substances, benzyl alcohol 5% lotion stuns these spiracles open, so that the mineral oil vehicle can obstruct them and the lice die from asphyxiation (Shionogi Pharma, Inc., 2010). This prescription product provides a non-neurotoxic pediculicidal alternative for parents who are concerned about the use of those agents.

Daily removal of lice and their nits from a child's hair may be accomplished with a metal nit comb. "Nit combing," considered a mechanical type of lice therapy, is helpful as an adjunctive measure, but most studies suggest that it is not as effective as chemical agents, especially when used as monotherapy (Diamantis et al., 2009; Ko & Elston, 2004). Nit combing after treatment with a pediculicide is helpful, because none of the pediculicidal agents are 100% ovicidal. Removal of nits is tedious and time consuming but may be attempted for aesthetic reasons, to decrease diagnostic confusion, or to decrease the chance of self-reinfestation (AAP, 2009). Several products have been suggested as helpful in loosening the cement that adheres nits to hair shafts. These include dilute vinegar, 8% formic acid, and some enzymatic nit removal systems.

Some systemic antihelminthic agents and antibiotics have been used off-label for the treatment of head lice. Use of these medications is generally considered only for severe or resistant infestations where topical medications have failed or are ineffective (AAP, 2009; Elston, 2005; Roberts, 2002). The antihelminthic agents reported have included albendazole, levamisole, and ivermectin (Akisu, Delibas, & Aksoy, 2006). Albendazole has been used in a single dose or as a 3-day course of 400 mg daily, with a repeated single dose of albendazole 400 mg after 1 week (Akisu et al., 2006). Levamisole at a dose of 3.5 mg/kg once daily was suggested to be effective against pediculosis upon administration for 10 days (Nutanson, Steen, Schwartz, & Janniger, 2008). Ivermectin, the most frequently considered of the antihelminthic drugs, is an oral agent that is FDA-approved for onchocerciasis and strongyloidiasis. It has been used in a single oral dose of 200 micrograms/kg, repeated in 7–10 days, and has been demonstrated to be effective against head lice (Dourmishev, Dourmishev, & Schwartz, 2005). However, given its potential neurotoxicity when crossing the blood-brain barrier, it has been recommended ivermectin be avoided in children weighing less than 15 kg. The FDA has not approved ivermectin as a pediculicidal agent (Dourmishev et al., 2005; Lebwohl et al., 2007; Roberts, 2002).

Trimethoprim/sulfamethoxazole (TMP/SMX), which reportedly kills symbiotic bacteria in the gut flora of the head louse thereby interfering with its ability to synthesize B vitamins, has been suggested as being effective against head lice, albeit not approved by the FDA for this use (AAP, 2009; Frankowski & Weiner, 2002). One small study suggested this antibiotic demonstrated synergistic activity when used in combination with permethrin 1%, when compared with either agent alone (Hipolito, Mallorca, Zuniga-Macaraig, Apolinario, & Wheeler-Sherman, 2001). Use of this agent should be balanced with the risk of severe, life-threatening allergic reactions (e.g., Stevens-Johnson or drug hypersensitivity syndromes).

Alternative Medications

The alternative treatments most often discussed for head lice are occlusive agents. The most commonly used products in this category are petroleum jelly, olive oil, butter, and fatcontaining mayonnaise. Un fortunately, lice have evolved mechanisms to evade the intended effect (asphyxiation) of these agents. In addition, these treatments tend to be messy and meet with low acceptance on the part of patients and parents. Shaving of the scalp has been proposed as a treatment option for lice, but may not be acceptable for school-aged children, especially girls.


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