What is the name of a lice medication?

Understanding Lice Infestations

What Are Lice?

Types of Lice

Lice are obligate ectoparasites that infest humans in distinct anatomical regions, each species displaying specific morphology and transmission patterns.

Head lice (Pediculus humanus capitis): inhabit scalp hair, lay eggs (nits) attached to hair shafts, spread primarily through direct head-to-head contact.
Body lice (Pediculus humanus humanus): reside in clothing seams and migrate to the skin to feed, transmitted via contaminated clothing or bedding; associated with poor hygiene conditions.
Pubic lice (Phthirus pubis), commonly called crabs: colonize the pubic region, perianal area, and occasionally facial hair, spread through sexual contact or close personal contact.
Animal‑derived lice (Haematopinus spp., Linognathus spp.): infest domestic animals such as dogs, cats, and livestock; occasional accidental human infestation occurs but does not constitute a primary human parasite.

Each type requires targeted therapeutic agents that act on the specific species’ biology, underscoring the necessity of accurate identification before treatment selection.

Life Cycle of Lice

The human head louse (Pediculus humanus capitis) completes its development in three distinct phases: egg, nymph, and adult.

Egg (nit) – Female lice embed each egg in the hair shaft within 0.5 mm of the scalp. The egg wall is cemented with a proteinaceous glue that resists removal. Incubation lasts 7–10 days at typical body‑temperature conditions.
Nymph – Upon hatching, the nymph resembles a miniature adult but lacks reproductive capability. Nymphs undergo three successive molts, each lasting approximately 2–3 days. During this period they feed frequently on blood to acquire the energy needed for growth.
Adult – Fully mature lice emerge after about 9–12 days from the egg. Adults live 20–30 days on the host, mate, and females lay 6–10 eggs per day. An adult female can produce up to 150 eggs during her lifespan, ensuring rapid population expansion.

The entire cycle, from egg to reproductive adult, can be completed in as little as 10 days under optimal conditions. This speed explains why infestations can double within a week if untreated. Effective pediculicidal treatment must target both live lice and newly hatched nymphs, while also addressing the resistant egg stage. Products containing neurotoxic agents such as permethrin or ivermectin are formulated to penetrate the egg shell and disrupt nerve transmission in nymphs and adults. Failure to eradicate the egg stage results in re‑infestation once surviving nymphs mature, underscoring the necessity of a comprehensive approach that aligns with the described life‑cycle timeline.

Symptoms of Lice Infestation

Lice infestation manifests primarily on the scalp and near the ears. It produces visible and tactile cues that distinguish it from other scalp conditions.

Small, translucent insects moving quickly across hair shafts.
Eggs (nits) attached firmly to hair strands, appearing as tiny, oval, yellow‑brown specks positioned within a few millimeters of the scalp.
Itching or irritation caused by bite‑induced inflammation, often intensifying after a few days.
Red or inflamed patches, sometimes accompanied by secondary bacterial infection from scratching.
A sensation of movement or “crawling” on the scalp, reported especially by children.

Identifying these signs directs the choice of an effective treatment product. Commonly prescribed options include permethrin‑based preparations, pyrethrin formulations, malathion lotions, and newer oral agents such as ivermectin. Selecting the correct medication eliminates the parasites and prevents recurrence.

Lice Medication: An Overview

Common Active Ingredients

Permethrin

Permethrin is a synthetic pyrethroid used to eliminate head‑lice infestations. It is the active ingredient in most over‑the‑counter lice treatments and is also prescribed for scabies.

The compound works by disrupting the nervous system of the parasite, causing paralysis and death. Formulations commonly available include:

1 % permethrin cream rinse (for head lice)
5 % permethrin lotion (for scabies)
0.5 % permethrin spray (for pet ectoparasites)

Application guidelines for head‑lice treatment typically require wetting the hair, applying the product, leaving it in place for 10 minutes, then rinsing thoroughly. A second treatment is advised 7–10 days later to eradicate any newly hatched lice.

Clinical studies report cure rates above 90 % when instructions are followed precisely. Adverse effects are generally limited to mild scalp irritation; systemic absorption is negligible. Contraindications include known hypersensitivity to permethrin or other pyrethroids.

Pyrethrin

Pyrethrin is a naturally derived insecticide employed to eradicate head‑lice infestations. Extracted from Chrysanthemum flowers, it attacks the nervous system of lice, causing rapid paralysis and death.

Key characteristics of pyrethrin‑based treatments:

Fast‑acting: kills adult lice and nymphs within minutes of contact.
Short residual activity: limited post‑application effect reduces risk of resistance.
Low toxicity to humans: safe for topical use on the scalp when applied according to label directions.
Available forms: shampoos, lotions, and sprays formulated for over‑the‑counter purchase.

Typical usage instructions include applying the product to dry hair, massaging into the scalp, leaving it on for the prescribed duration (often 10 minutes), then rinsing thoroughly. A repeat application after 7–10 days addresses newly hatched lice that survived the initial treatment.

Regulatory agencies classify pyrethrin as an approved lice remedy, permitting sales without prescription in many regions. Users should avoid excessive exposure, keep the product away from eyes, and store it out of reach of children.

Malathion

Malathion is an organophosphate insecticide formulated for the treatment of head‑lice infestations. It works by inhibiting acetylcholinesterase, leading to paralysis and death of the lice. The medication is supplied as a 0.5 % lotion applied to dry hair, left for ten minutes, then rinsed thoroughly.

Key characteristics of Malathion for pediculosis:

Efficacy: kills both adult lice and newly hatched nymphs; resistance is uncommon compared with pyrethrin‑based products.
Safety profile: approved for use in children six months and older; systemic absorption is minimal, but contraindicated for individuals with known organophosphate hypersensitivity.
Application guidelines: repeat treatment after 7–10 days to eliminate any newly hatched lice that survived the first dose.
Regulatory status: FDA‑approved as a prescription medication in the United States; available over the counter in several countries under brand names such as Ovide and LiceMD.

Clinical use of Malathion requires adherence to dosage instructions, avoidance of contact with eyes, and thorough washing of hands after application. Monitoring for skin irritation or allergic reactions is recommended, with discontinuation if severe symptoms develop.

Ivermectin (Topical)

Ivermectin in its topical formulation is a prescription‑only agent used to eradicate head‑lice infestations. Applied as a 0.5 % cream or lotion, it penetrates the exoskeleton of lice, binding to glutamate‑gated chloride channels and causing paralysis and death of the parasite.

The typical regimen involves a single application to dry hair, left on for 10 minutes before washing off. A repeat treatment after 7 days eliminates any newly hatched nymphs that survived the first dose. Studies report cure rates above 90 % when both applications are completed as directed.

Key points for clinicians:

Indicated for patients with confirmed pediculosis capitis, including those resistant to pyrethroids.
Contraindicated in individuals with known hypersensitivity to ivermectin or its excipients.
Common adverse effects: mild scalp irritation, erythema, or transient itching.
Systemic absorption is minimal; however, caution is advised for pregnant or lactating women, and for children under 15 kg.

Ivermectin topical provides an effective, single‑visit option for managing lice, especially when resistance to traditional insecticides limits treatment success.

Spinosad

Spinosad is the active ingredient in a prescription‑only treatment for head lice. Marketed under the name Natroba, it is applied as a 0.9 % lotion to dry hair, left for 10 minutes, then rinsed. The compound disrupts the nervous system of lice, causing rapid paralysis and death without affecting human cells.

Key characteristics:

Mechanism of action: Binds to nicotinic acetylcholine receptors in lice, leading to uncontrolled nerve firing.
Efficacy: Clinical trials report a cure rate of approximately 95 % after a single application, eliminating both live insects and viable eggs.
Safety profile: Minimal skin irritation; contraindicated for children under six months or those with known hypersensitivity to spinosad.
Regulatory status: Approved by the U.S. Food and Drug Administration (FDA) for over‑the‑counter sale in many regions, though some countries require a prescription.

Spinosad’s single‑dose regimen simplifies treatment compared with traditional pediculicides that demand multiple applications. Its effectiveness against resistant lice strains makes it a valuable option for clinicians and consumers seeking a reliable solution to infestations.

Benzyl Alcohol

Benzyl alcohol is an FDA‑approved pediculicide used to eradicate head‑lice infestations. The formulation, marketed under the name Ulesfia, contains 5 % benzyl alcohol in a petroleum‑based vehicle, delivering a topical solution that suffocates lice without affecting the eggs.

The compound acts as a neurotoxin for adult lice. By penetrating the respiratory system of the parasite, it interferes with neural transmission, leading to rapid immobilization and death within 30 minutes of exposure. The treatment does not contain insecticidal chemicals that target the nervous system of mammals, reducing systemic absorption.

Clinical studies report a single 10‑minute application followed by a thorough rinse eliminates 95 %–98 % of live lice. The regimen includes a repeat treatment after seven days to address any newly hatched nymphs that survived the initial exposure. No resistance has been documented, making benzyl alcohol a reliable option when other pediculicides fail.

Safety considerations:

Approved for children aged six months and older.
Contraindicated in individuals with known hypersensitivity to benzyl alcohol or petroleum derivatives.
Minor skin irritation reported in <2 % of users; no systemic toxicity observed at recommended concentrations.
Use with caution on broken skin or open lesions.

Benzyl alcohol thus provides an effective, non‑neurotoxic alternative for managing head‑lice infestations, supported by regulatory approval and peer‑reviewed efficacy data.

Over-the-Counter (OTC) Treatments

How OTC Medications Work

Over‑the‑counter (OTC) lice treatments rely on chemicals that disrupt the nervous system of the parasite. The most common agents are synthetic pyrethroids, such as permethrin, and natural pyrethrins derived from chrysanthemum flowers. Both groups bind to voltage‑gated sodium channels on nerve membranes, causing prolonged depolarization, paralysis, and death of the insect.

Other OTC options include malathion, an organophosphate that inhibits acetylcholinesterase, leading to accumulation of acetylcholine and continuous nerve impulse transmission. Dimethicone, a silicone‑based fluid, works mechanically by coating lice and suffocating them, without chemical toxicity.

Typical OTC formulations combine an active ingredient with a carrier that enhances skin penetration and ensures even distribution:

1% permethrin lotion – applied to dry hair, left for 10 minutes, then rinsed.
0.5% malathion shampoo – applied to damp hair, left for 8 hours, then washed.
4% dimethicone spray – applied to wet hair, left for 10 minutes, then combed.

Efficacy depends on correct dosage, thorough coverage of the scalp, and adherence to the product’s timing instructions. Re‑treatment after 7–10 days eliminates newly hatched nymphs that survived the initial exposure.

Proper Application of OTC Treatments

Over‑the‑counter lice remedies, such as permethrin‑based sprays or pyrethrin lotions, require precise use to eliminate infestations and prevent re‑infestation. Follow these steps for optimal results.

Apply the product to dry hair, saturating the scalp from roots to tips.
Leave the medication on for the time specified on the label, typically 10 minutes for sprays and 30 minutes for lotions.
Rinse thoroughly with warm water, avoiding hot water that may degrade the active ingredient.
Comb the hair with a fine‑toothed lice comb while still damp, removing dead insects and nits.
Discard the comb after each pass or clean it with hot, soapy water between uses.
Wash clothing, bedding, and personal items in hot water (≥130 °F) and dry on high heat for at least 20 minutes.

Repeat the treatment after 7–10 days, as directed, to eradicate any newly hatched lice that survived the first application. Ensure that all household members are screened and treated if necessary to break the transmission cycle.

Potential Side Effects of OTC Medications

Over‑the‑counter lice treatments typically contain permethrin, pyrethrin, or dimethicone as active ingredients. These compounds eradicate head‑lice infestations through neurotoxic or physical mechanisms, and are available without prescription in pharmacies and online retailers.

Potential adverse reactions include:

Skin irritation: redness, itching, or burning at the application site.
Allergic response: hives, swelling, or respiratory difficulty after exposure to pyrethrin‑based products.
Eye injury: accidental contact may cause conjunctival redness or pain.
Systemic effects: rare cases of nausea, dizziness, or headache following extensive absorption.

Users should follow label instructions precisely, apply the product only to dry hair, and avoid contact with broken skin or mucous membranes. If symptoms persist beyond 24 hours or worsen, discontinue use and seek medical evaluation.

Prescription Medications

When to Consider Prescription Treatments

Prescription lice treatments become necessary when over‑the‑counter options fail to eradicate the infestation or when specific risk factors are present. Failure is indicated by live lice persisting after two complete treatment cycles, or by rapid reinfestation despite correct application. Resistance to common pyrethrin‑based shampoos also signals the need for a stronger agent.

Consider a prescription formulation if any of the following conditions apply:

The patient is under six months of age, for whom most topical OTC products are contraindicated.
There is a documented allergy to ingredients in non‑prescription preparations.
Previous treatment with permethrin, pyrethrins, or similar agents did not eliminate live lice.
The infestation includes a high lice load that overwhelms standard dosing recommendations.
The individual has a compromised immune system, increasing the risk of secondary skin infections.

Typical prescription options include ivermectin oral tablets, malathion 0.5 % lotion, benzyl alcohol 5 % lotion, and spinosad 0.9 % suspension. Each medication requires a physician’s evaluation to confirm suitability, dosage, and safety based on age, weight, and medical history. Prompt medical consultation ensures the selected drug addresses the infestation effectively while minimizing adverse effects.

How Prescription Medications Differ

Prescription medications are regulated by agencies that require a licensed prescriber’s authorization. They differ from over‑the‑counter products in several measurable ways: formulation strength, required medical supervision, and legal classification.

Lice treatment that requires a prescription is typically a neurotoxic agent applied to the scalp. The most commonly prescribed brand is Nix® (permethrin 1 %); an alternative is Kwell™ (spinosad 0.9 %), both approved only with a doctor’s order. These agents contain concentrations higher than non‑prescription options, ensuring efficacy against resistant lice strains.

Key distinctions among prescription therapies include:

Active ingredient potency – prescription formulas deliver doses that exceed OTC limits, targeting resistant infestations.
Dosage schedule – some require a single application, others a repeat after 7–10 days, as indicated on the prescription label.
Safety monitoring – prescribers assess patient history for allergies or contraindications before dispensing.
Insurance coverage – prescription products may be reimbursed under health plans, whereas OTC items are paid out‑of‑pocket.

Understanding these differences helps clinicians select the appropriate lice medication and informs patients about the regulatory and clinical implications of using a prescribed treatment versus an over‑the‑counter alternative.

Potential Side Effects of Prescription Medications

Prescription treatments for head‑lice infestations, such as permethrin 1% cream rinse or ivermectin tablets, carry a range of possible adverse reactions. Most patients experience mild, transient effects, but clinicians must recognize less common, serious events.

Common reactions include:

Skin irritation, redness, or itching at the application site
Burning or stinging sensations during or after use
Temporary hair loss when the product is left on the scalp too long

Less frequent but clinically relevant side effects are:

Allergic dermatitis presenting as rash, swelling, or hives
Systemic symptoms such as nausea, dizziness, or headache (more typical with oral ivermectin)
Neurologic manifestations, including tremor or seizures, reported in rare cases of overdose or hypersensitivity

Risk factors that increase the likelihood of adverse events comprise pre‑existing skin conditions, concurrent use of other topical agents, and improper application techniques. Monitoring should focus on the onset, severity, and duration of symptoms; persistent or worsening reactions warrant immediate medical evaluation and possible discontinuation of therapy.

Non-Pharmacological Approaches to Lice Treatment

Manual Removal (Combing)

Manual removal, often called combing, is a non‑chemical approach to eliminating head‑lice infestations. The technique relies on a fine‑toothed lice comb to physically extract live lice and nits from hair shafts, reducing reliance on topical insecticides.

The procedure follows a consistent sequence:

Dampen hair with water or a conditioning agent to ease comb movement.
Section hair into manageable strands, typically 1–2 cm wide.
Starting at the scalp, draw the comb slowly toward the hair tip, ensuring each tooth contacts the hair shaft.
After each pass, wipe the comb on a tissue or rinse it in warm water to remove captured insects.
Repeat the process on every section, covering the entire head.
Perform the routine daily for at least seven days, then twice weekly for an additional two weeks to catch any newly hatched lice.

Advantages of combing include immediate visual confirmation of removed pests, avoidance of allergic reactions, and suitability for infants and pregnant individuals. Limitations involve the need for disciplined, repeated sessions and the possibility of missing nits concealed close to the scalp.

When compared with pharmaceutical lice treatments, combing offers a mechanical solution that does not contribute to resistance development. However, chemical products such as permethrin or ivermectin provide faster eradication in a single application, albeit with a higher risk of skin irritation and potential resistance. Combining manual removal with a mild, approved pediculicide can enhance overall efficacy, especially in severe infestations.

Environmental Control

Cleaning Personal Items

Effective lice eradication requires more than topical treatment; it also demands thorough sanitation of personal belongings. Residual eggs, known as nits, can survive on combs, hats, pillowcases, and clothing, re‑infesting the scalp after medication application.

To support the medication named permethrin, follow these steps:

Wash fabrics in hot water (minimum 130 °F/54 °C) and dry on high heat for at least 20 minutes.
Soak hair‑care tools (combs, brushes, rollers) in a solution of 0.5 % sodium hypochlorite for 10 minutes, then rinse and air‑dry.
Seal non‑washable items (e.g., stuffed toys) in a sealed plastic bag for two weeks; the prolonged isolation kills viable nits.
Vacuum carpets, upholstery, and vehicle seats; discard vacuum bags immediately after use.

Completing these procedures eliminates sources of reinfestation, ensuring the lice medication works as intended and reduces the likelihood of recurrence.

Preventing Reinfestation

Effective lice control hinges on more than selecting the correct treatment; it requires a systematic approach to prevent a second outbreak. After applying a medication such as permethrin, pyrethrin, or malathion, follow these steps to eliminate residual eggs and reduce the risk of re‑infestation.

Wash all worn clothing, bedding, and towels in hot water (≥130 °F) and dry on high heat for at least 30 minutes.
Seal non‑washable items in sealed plastic bags for two weeks to suffocate any surviving nits.
Vacuum carpets, upholstered furniture, and vehicle seats; discard vacuum bags or clean canisters immediately.
Comb hair with a fine‑toothed nit comb every 2–3 days for two weeks, removing any newly hatched lice.
Inspect all close contacts—family members, classmates, caregivers—and treat anyone with active infestation or visible nits.
Advise children to avoid head‑to‑head contact, sharing hats, combs, or hair accessories for the duration of treatment and for at least one week afterward.

Consistent application of these measures eliminates residual parasites, interrupts the life cycle, and safeguards against recurrence.

Choosing the Right Lice Medication

Factors to Consider

Age of the Individual

Lice treatment products are selected based on the patient’s age because safety and efficacy differ across developmental stages. Regulatory agencies approve specific formulations for infants, children, and adults, and manufacturers label each product with the appropriate age range.

Common over‑the‑counter lice medications and their minimum age requirements:

Permethrin 1% cream rinse – approved for use in children 2 months and older; also suitable for adults.
Pyrethrins with piperonyl‑butoxide – cleared for children 2 years and older; adult use permitted.
Spinosad 1% lotion – indicated for children 4 years and older; effective for adults.
Ivermectin 0.5% lotion – prescribed for individuals 6 months and older; often used when other agents fail.
Malathion 0.5% liquid – recommended for children 6 years and older; adult application allowed.

Prescribing clinicians must verify that the chosen product matches the patient’s age bracket, observe any contraindications, and follow the dosage instructions on the label. Failure to adhere to age specifications can increase the risk of adverse reactions or reduce treatment success.

Severity of Infestation

The intensity of a head‑lice outbreak determines the appropriate therapeutic product.

Mild – fewer than 10 live lice, limited egg clusters, confined to a single individual.
Moderate – 10‑30 lice, multiple egg masses, spread to close contacts.
Severe – over 30 lice, extensive egg deposition across several family members or a group setting.

Medication selection aligns with these levels. For mild cases, a single‑application topical agent containing 1 % permethrin or 0.5 % pyrethrin often suffices. Moderate infestations may require a higher‑concentration preparation, such as 1 % ivermectin lotion, combined with a second treatment 7–10 days later to eradicate newly hatched nymphs. Severe outbreaks typically demand a prescription‑only formulation—e.g., 0.5 % malathion or oral ivermectin—administered in multiple doses and accompanied by thorough combing of wet hair to remove eggs.

Accurate assessment of infestation severity ensures the chosen lice remedy achieves complete eradication while minimizing unnecessary exposure to stronger agents.

Presence of Allergies or Sensitivities

When a person shows signs of allergy or heightened skin sensitivity, selecting an appropriate pediculicide requires careful evaluation of active ingredients and known irritant profiles.

Allergic reactions to common lice treatments most often involve pyrethrins, permethrin, and benzyl alcohol. Contact dermatitis may appear within hours, presenting as redness, itching, or swelling. Individuals with a history of insecticide sensitivity should avoid products containing these compounds.

Medications with lower allergenic potential include:

Ivermectin lotion (0.5 %); minimal skin irritation reported, suitable for patients with pyrethroid sensitivity.
Spinosad suspension (0.9 %); low incidence of hypersensitivity, effective against resistant lice.
Malathion (0.5 %); useful when other agents fail, but contraindicated in individuals with known organophosphate allergy.

Before application, a patch test is advisable: apply a small amount of the product to a discreet skin area, wait 24 hours, and observe for any adverse response. Positive results necessitate choosing an alternative formulation.

If systemic allergy signs such as hives, breathing difficulty, or swelling develop after treatment, discontinue use immediately and seek medical attention. Documentation of the specific reaction assists health professionals in recommending a safe, effective lice eradication regimen for future infestations.

Previous Treatment Failures

Previous attempts to eradicate head lice frequently end without success. Failure often stems from using products that lack sufficient active ingredient, applying the treatment for an inadequate duration, or neglecting thorough combing of the hair. Resistance to common pediculicides, such as permethrin, also contributes to persistent infestations. Incomplete coverage of the scalp, especially in dense or curly hair, leaves viable lice and nits, allowing the population to rebound quickly. Re‑infestation from untreated household members or close contacts further undermines initial therapy.

Typical causes of unsuccessful outcomes include:

Sub‑therapeutic concentration of the insecticide.
Shortened exposure time contrary to label instructions.
Absence of a systematic nit‑removal process.
Use of products past their expiration date.
Presence of resistant lice strains.

Recognizing these pitfalls clarifies why selecting an effective medication, such as a prescription‑only 1% ivermectin lotion, becomes essential for definitive control.

Consulting a Healthcare Professional

When dealing with a head‑lice infestation, direct consultation with a qualified health provider ensures the selection of an appropriate, evidence‑based treatment. The professional can confirm the diagnosis, evaluate any drug resistance in the local population, and consider patient‑specific factors such as age, allergies, and concurrent medications.

Key reasons to seek professional advice include:

Verification that the condition is indeed pediculosis capitis.
Identification of the most effective FDA‑approved topical agent for the current resistance patterns.
Assurance that the chosen product is safe for the patient’s age group and health status.
Guidance on correct dosing, application timing, and retreatment intervals.

Typical steps for a patient are:

Arrange an appointment with a primary‑care physician, dermatologist, or pediatrician.
Present a clear history of the infestation, including previous over‑the‑counter attempts.
Disclose any known drug sensitivities, skin conditions, or chronic illnesses.
Request the specific medication name, dosage form, and brand or generic options.
Follow the provider’s instructions for use, including washing of clothing and bedding.

During the visit, the clinician will likely recommend one of the following agents, depending on the assessment: permethrin 1 % lotion, pyrethrin‑based shampoo, ivermectin 0.5 % lotion, or malathion 0.5 % lotion. They will explain the proper application procedure, required repeat treatment, and potential adverse effects such as skin irritation or rare allergic reactions. Compliance with these directives maximizes eradication success and minimizes the risk of reinfestation.