How do you treat head lice?

Understanding Head Lice

What Are Head Lice?

Life Cycle of Lice

Head lice (Pediculus humanus capitis) complete their development in three distinct stages: egg, nymph, and adult. Female lice attach each egg to a hair shaft within 1 mm of the scalp. The egg, commonly called a nit, requires 7–10 days to hatch under optimal temperature (30–32 °C) and humidity conditions.

After emergence, the nymph undergoes three successive molts. Each molt lasts approximately 5–7 days, during which the insect increases in size but remains unable to reproduce. By the end of the third molt, the nymph reaches adult morphology and becomes capable of oviposition.

Adult lice survive up to 30 days on a host. A fertilized female can lay 6–10 eggs per day, accumulating roughly 100 eggs over her lifespan. Adults feed several times daily on blood, causing irritation and facilitating the spread of additional eggs through direct head-to-head contact.

Understanding the timing of each stage informs effective intervention. Treatments that target both live insects and newly hatched nymphs must be applied within the 7–10‑day window after egg deposition, and a second application is recommended 7–10 days later to eliminate any survivors that emerged from eggs protected during the initial treatment.

Common Symptoms

Head lice infestations manifest through a distinct set of observable signs that prompt treatment. The presence of live insects or their eggs on the scalp is the most direct indicator, often detected by close inspection or a fine-toothed comb.

Small, white or tan nits firmly attached to hair shafts, especially near the scalp
Live lice, measuring 2–3 mm, moving quickly across the hair or skin
Itching or irritation caused by allergic reactions to lice saliva
Redness or small sores resulting from scratching
Unusual feeling of movement or crawling on the scalp, sometimes described as a “tingling” sensation

These symptoms typically appear within one to two weeks after initial contact with an infested individual and may intensify if the infestation persists. Prompt identification enables effective intervention.

How Head Lice Are Transmitted

Misconceptions About Transmission

Misunderstandings about how head‑lice spread often hinder effective control. Many people assume that lice are transmitted through casual contact such as shaking hands, hugging, or sharing food, but these routes do not support lice survival. The insects cling to hair shafts and require direct head‑to‑head contact to move between hosts.

Common false beliefs include:

Lice can crawl onto clothing, towels, or bedding and infest a person later.
Pets or insects such as fleas act as carriers for head‑lice.
A single brief touch with an infested individual is enough for transmission.

Scientific evidence shows that transmission occurs almost exclusively through prolonged head‑to‑head contact, typical in schools, sports teams, and close family interactions. Lice cannot survive more than 24 hours off a human scalp, and they do not jump or fly, limiting their ability to spread via inanimate objects.

Correcting these misconceptions streamlines treatment strategies. Eliminating unnecessary decontamination of clothing or household items reduces wasted effort and focuses resources on thorough combing, appropriate topical agents, and repeated inspections. Understanding the true mode of spread ensures that preventive measures target the actual risk factors, thereby improving eradication outcomes.

Treatment Options

Over-the-Counter (OTC) Treatments

Pyrethrin-Based Products

Pyrethrin-based products contain natural extracts derived from Chrysanthemum flowers. The active compounds disrupt the nervous system of lice, causing rapid paralysis and death. Formulations typically combine pyrethrins with piperonyl butoxide, a synergist that enhances insecticidal activity.

Application involves applying the lotion or shampoo to dry hair, ensuring thorough coverage of the scalp and all strands. After a prescribed exposure period—usually 10 minutes—treatment is rinsed out. A second application 7–10 days later eliminates newly hatched insects before they mature. Follow manufacturer instructions precisely; over‑application does not increase efficacy and may increase irritation.

Safety considerations include:

Minimum age: many products are approved for children 2 months and older; infants younger than this require alternative agents.
Skin sensitivity: mild itching, redness, or a transient burning sensation may occur; discontinue use if severe reactions develop.
Resistance: repeated use in areas with documented pyrethrin‑resistant lice can reduce effectiveness; rotating to a different class of pediculicide may be necessary.

Advantages of pyrethrin formulations:

Rapid knock‑down of live lice within minutes.
Natural origin may appeal to users seeking botanical options.
Generally inexpensive and widely available.

Limitations:

Limited efficacy against resistant strains.
Not suitable for individuals with known insecticide allergies.
Requires precise timing of repeat dose to prevent re‑infestation.

When incorporated into a comprehensive lice‑management plan—combining proper combing, washing of bedding, and environmental cleaning—pyrethrin-based products provide a reliable chemical tool for eliminating head‑lice infestations.

Permethrin-Based Products

Permethrin-based products are the most widely recommended first‑line agents for managing head‑lice infestations. The active ingredient, permethrin 1 %, is a synthetic pyrethroid that disrupts the nervous system of lice, leading to rapid paralysis and death. Formulations include lotions, shampoos, and sprays specifically labeled for pediculicide use.

Application instructions must be followed precisely to achieve optimal efficacy. A typical regimen involves:

Applying the product to dry hair, ensuring thorough coverage from scalp to hair tips.
Leaving the preparation on for the manufacturer‑specified duration, usually 10 minutes.
Rinsing thoroughly with lukewarm water, then combing with a fine‑toothed nit comb to remove dead insects and nits.
Repeating the treatment after 7–10 days to eliminate newly hatched lice that survived the initial exposure.

Safety considerations include avoiding contact with eyes, limiting exposure for infants under two months, and confirming that the user does not have a known allergy to permethrin. Systemic absorption is minimal; adverse effects are typically limited to mild scalp irritation or transient itching.

Resistance to permethrin has been documented in some regions. When treatment fails after two consecutive applications, switching to an alternative class of pediculicide (e.g., ivermectin or dimethicone) is advisable, accompanied by repeat mechanical removal of nits. Continuous monitoring of infestation status for at least four weeks post‑treatment helps confirm eradication and prevents reinfestation.

Application Instructions

Effective treatment of head lice depends on precise application of the chosen product. Follow each step to ensure maximum efficacy and minimize re‑infestation.

Verify the product’s expiration date and read the label for age restrictions and contraindications.
Gather necessary items: fine‑tooth comb, disposable gloves, old towels, and a timer.
Wash the affected person’s hair with regular shampoo; rinse thoroughly and towel‑dry until damp, not wet.
Apply the lice‑killing formulation evenly from scalp to hair tips, using the supplied applicator or a spray bottle. Ensure full coverage of the scalp, behind the ears, and at the nape.
Leave the product on for the time specified on the label (typically 10–15 minutes). Set a timer to avoid under‑ or over‑exposure.
Rinse hair with lukewarm water, removing all residue. Do not use conditioner unless the label permits.
While hair remains damp, comb through each section with a fine‑tooth lice comb, starting at the scalp and pulling toward the ends. Clean the comb after each pass with a disposable wipe or alcohol.
Repeat the combing process at least twice daily for seven days to capture any newly hatched nymphs.

After treatment, wash all bedding, clothing, and personal items in hot water (≥ 130 °F) or place them in a sealed bag for two weeks. Inspect family members and treat any additional cases promptly. Maintain the same application schedule for the recommended repeat dose, usually seven days after the first treatment, to break the life cycle completely.

Prescription Treatments

Malathion Lotion

Malathion lotion is a prescription‑strength pediculicide formulated for topical use on the scalp and hair. It contains 0.5 % malathion, an organophosphate insecticide that disrupts the nervous system of lice, leading to paralysis and death. The product is approved for patients aged six months and older, including those with resistant infestations.

Application requires thorough wet combing of the hair, followed by a uniform coating of the lotion from the scalp to the tips of the hair. The solution must remain on the scalp for at least eight hours, after which it is rinsed off with warm water and a mild shampoo. A second treatment, scheduled seven days later, eliminates newly hatched nymphs that survived the first exposure.

Key safety considerations:

Do not apply to broken or inflamed skin.
Avoid contact with eyes; immediate irrigation is necessary if exposure occurs.
Pregnant or nursing individuals should consult a healthcare provider before use.
Keep away from pets and children; store at room temperature, protected from light.

Effectiveness studies report cure rates exceeding 90 % when the regimen is followed precisely. Resistance to malathion remains low compared with pyrethroid agents, making it a reliable option for persistent or recurrent infestations.

Ivermectin Lotion

Ivermectin lotion is a topical medication approved for the eradication of head‑lice infestations. The active ingredient, ivermectin, binds to glutamate‑gated chloride channels in the parasite’s nervous system, causing paralysis and death of the lice and their eggs.

Application guidelines are as follows:

Apply a thin layer of lotion to dry, clean hair and scalp, covering the entire affected area.
Leave the product in place for the time specified on the label, typically 10 minutes.
Rinse thoroughly with water, then shampoo as usual.
Repeat the treatment after seven days to eliminate any newly hatched insects.

Clinical studies report cure rates of 85 %–95 % after a single application, with the follow‑up dose ensuring residual hatching is addressed. Adverse effects are generally mild, including transient scalp irritation, erythema, or itching; systemic absorption is minimal, making the lotion suitable for children over six months of age when prescribed.

When selecting a treatment regimen for pediculosis capitis, ivermectin lotion offers an alternative to traditional neurotoxic agents such as permethrin, especially in cases of resistance. Prescription is required in most jurisdictions, and the product should be stored at room temperature, protected from light, to maintain potency.

Spinosad Suspension

Spinosad suspension is a prescription‑only topical medication specifically formulated for the eradication of head‑lice infestations. The active ingredient, spinosad, is a bacterial fermentation product that disrupts the nervous system of lice, leading to rapid paralysis and death. Unlike older neurotoxic agents, spinosad targets nicotinic acetylcholine receptors, reducing the likelihood of cross‑resistance with pyrethrins or malathion.

Application guidelines require thorough wet combing of dry hair to remove nits before treatment. The suspension is applied to the scalp and hair, covering the entire area from the forehead to the nape of the neck. After a 10‑minute exposure, the product is rinsed off with warm water. A single treatment typically achieves >99 % lice elimination; a repeat application after 7 days addresses any newly hatched nits that escaped initial removal.

Key safety considerations include:

Avoid use on children under 4 years of age.
Do not apply to broken skin or irritated scalp.
Pregnant or breastfeeding individuals should consult a healthcare professional before use.

Clinical studies demonstrate superior efficacy compared to traditional insecticides, with minimal reports of adverse skin reactions. Spinosad’s novel mode of action also mitigates the spread of resistant lice strains, making it a valuable option for patients with prior treatment failures. Availability is limited to pharmacies with a valid prescription, ensuring appropriate medical oversight.

Non-Chemical Approaches

Wet Combing Method

Wet combing, also known as the “metallic” or “wet” method, removes live lice and nits from hair without chemicals. The technique relies on a fine-toothed comb, a conditioner or oil to immobilize insects, and systematic brushing.

To perform the method, follow these steps:

Apply a generous amount of lubricating conditioner, mineral oil, or a specialized lice‑removal product to damp hair. Allow the solution to sit for several minutes so that lice lose mobility.
Section the scalp into manageable portions using clips or hair ties. Work from the scalp outward, keeping the comb vertical.
Starting at the root, pull the comb through each section slowly, ensuring the teeth reach the skin. After each pass, wipe the comb on a tissue or rinse it in warm water to remove captured lice and eggs.
Repeat the process on every section, covering the entire head. A single session typically requires 10–15 minutes for children’s hair and up to 30 minutes for longer or thicker hair.
Dispose of any captured insects by flushing them down the toilet or sealing them in a plastic bag.
Wash the hair thoroughly after treatment to remove residual conditioner or oil.

Repeat the procedure every 3–4 days for two weeks. This schedule aligns with the life cycle of head lice, preventing newly hatched nymphs from maturing and reproducing.

Advantages of wet combing include:

No exposure to pesticides or irritants.
Immediate visual confirmation of removed insects.
Suitability for infants, pregnant individuals, and those with sensitivities to topical medications.

Limitations comprise the time‑intensive nature of the process and the need for consistent repetition. Combining wet combing with regular laundering of bedding, clothing, and personal items enhances overall success in eliminating an infestation.

Suffocation Treatments

Suffocation treatments aim to block the respiratory openings of lice, causing them to die without the need for insecticides. The method relies on coating the hair and scalp with a substance that prevents oxygen exchange.

Apply a thick, occlusive agent such as mineral oil, petroleum jelly, or a silicone‑based lotion. Ensure coverage from the scalp to the tips of all hair strands.
Leave the product in place for a minimum of eight hours; overnight application is common because it maximizes exposure while the person sleeps.
After the prescribed period, remove the residue with a fine‑toothed comb. Comb the hair in sections, starting at the roots and pulling the comb through to the ends. Repeat until no live insects are visible.
Wash the hair thoroughly with a mild shampoo to eliminate remaining oil and any dead lice or nits.

Effectiveness depends on complete coverage and sufficient exposure time. Partial application or early removal can allow some lice to survive. The method does not dissolve nits; manual removal with a comb remains necessary.

Safety considerations include avoiding the use of petroleum products on infants under two months, individuals with eczema or dermatitis, and on scalp wounds. Oil‑based preparations can stain fabrics; protect bedding and clothing during treatment.

When used correctly, suffocation agents provide a chemical‑free alternative that reduces the risk of resistance and allergic reactions associated with traditional insecticidal shampoos.

Essential Oils and Home Remedies

Essential oils provide a chemical approach to lice control without prescription medication. Tea‑tree oil, diluted to 0.5 % in a carrier such as coconut oil, kills nymphs and adult insects after a 30‑minute exposure. Lavender oil, combined with a 1 % concentration, reduces egg viability when applied to the scalp for 15 minutes before rinsing. Peppermint oil, at 0.3 % concentration, offers a repellent effect that discourages re‑infestation. Eucalyptus and rosemary oils, each at 0.4 % dilution, have demonstrated adult lice mortality in laboratory studies. Neem oil, applied neat or mixed with a carrier, interferes with lice respiration and may be left on the hair for up to one hour. For all oils, a patch test on a small skin area reduces the risk of irritation; avoid use on children under two years.

Home‑based methods complement essential‑oil treatments. Wet‑combing with a fine‑toothed nit comb, performed on damp hair after applying a lubricant such as olive oil, removes live lice and viable eggs. A 1 % vinegar solution, sprayed onto the scalp and left for 10 minutes, loosens nits, facilitating removal with a comb. Applying a thick layer of mayonnaise or petroleum jelly, covering the hair for 8–12 hours, suffocates insects; subsequent thorough washing eliminates residues. Baking soda, mixed with water to form a paste and applied for 20 minutes, dehydrates lice. Each method requires repeated application every 3–4 days for at least two weeks to eradicate newly hatched nymphs.

Combining diluted essential oils with a systematic wet‑combing schedule maximizes efficacy. Begin with a 30‑minute oil treatment, rinse, then comb through hair while still damp. Repeat the cycle for seven days, followed by a second series after 10 days to capture any remaining hatchlings. Ensure thorough cleaning of combs, clothing, and bedding after each session to prevent re‑colonization. If symptoms persist or severe irritation occurs, consult a healthcare professional for alternative therapeutic options.

Post-Treatment Care and Prevention

Checking for Nits and Reinfestation

Follow-Up Treatments

Effective control of head‑lice infestations requires more than a single application of a pediculicide. After the initial treatment, a structured follow‑up protocol prevents re‑infestation and eliminates surviving nits.

A second treatment should be administered 7–10 days after the first. This interval coincides with the life cycle of lice, ensuring that any newly hatched nymphs are killed before they can lay eggs. Use the same product or a complementary formulation, following the manufacturer’s instructions precisely.

Regular inspection of the scalp and hair is essential during the follow‑up period. Perform visual checks every 2–3 days for at least three weeks. Remove visible nits with a fine‑tooth comb, working from the scalp outward. Discard or decontaminate combs, brushes, hats, pillowcases, and bedding after each use.

If live lice are observed after the second application, repeat a third treatment after another 7 days. Persistent cases may require prescription‑strength medication or a consultation with a healthcare professional.

Key components of a follow‑up regimen:

Second application 7–10 days post‑initial treatment
Daily scalp inspections for three weeks
Mechanical removal of nits with a fine‑tooth comb
Laundering or sealing of personal items (clothing, bedding) in hot water or a freezer for 48 hours
Additional treatment cycles if live lice remain

Adhering to this schedule eliminates the infestation and reduces the likelihood of recurrence.

Environmental Cleaning

Effective elimination of head‑lice infestations extends beyond direct treatment of the scalp. Removing viable eggs and nymphs from the surrounding environment reduces the chance of reinfestation.

Launderable items should be washed in hot water (minimum 130 °F/54 °C) and dried on high heat for at least 20 minutes. Items that cannot be laundered—such as hats, scarves, hair accessories, and pillowcases—must be sealed in airtight plastic bags for two weeks, the period during which lice cannot survive without a host.

Thoroughly clean surfaces that may contact hair:

Vacuum carpets, upholstery, and floor mats; discard the vacuum bag or clean the canister immediately after use.
Wipe hard surfaces (desk tops, armrests, doorknobs, light switches) with an EPA‑registered disinfectant or a solution of 1 % bleach (10 ml bleach per liter of water).
Spray hair‑brushes, combs, and hair‑dryers with the same disinfectant; allow to air‑dry before reuse.

Non‑launderable bedding and mattresses should be exposed to direct sunlight for several hours or treated with a steam cleaner that reaches at least 212 °F (100 °C).

Finally, isolate personal items (e.g., hair clippers, styling tools) in a sealed container for 48 hours, then disinfect before returning to regular use. Consistent application of these environmental measures, combined with appropriate topical therapy, maximizes the likelihood of complete eradication.

Preventing Future Infestations

Education and Awareness

Education equips caregivers, teachers, and children with accurate information about head‑lice detection, prevention, and treatment. Clear guidance reduces misdiagnosis, limits unnecessary chemical use, and encourages prompt, effective response.

Essential elements of an awareness program include:

Identification criteria: visual signs on scalp, nits attached within 1 cm of the hair shaft, and common symptoms such as itching.
Treatment options: over‑the‑counter pediculicides, prescription medications, and non‑chemical methods like wet combing; instructions on correct application, dosage, and retreatment intervals.
Resistance awareness: recognition that some lice populations no longer respond to certain insecticides; recommendation to rotate products or use alternative approaches when failure occurs.
Hygiene practices: regular hair inspections, avoidance of sharing personal items, and proper laundering of clothing and bedding after treatment.
Follow‑up procedures: scheduled re‑examinations 7–10 days post‑treatment to confirm eradication and address reinfestation promptly.

Effective dissemination relies on multiple channels: school newsletters, parent‑teacher meetings, community health workshops, and digital resources such as instructional videos. Materials should present step‑by‑step guidance, common pitfalls, and FAQ sections to address misconceptions.

Schools play a pivotal role by integrating head‑lice education into health curricula, establishing clear reporting protocols, and coordinating with local health services for rapid access to treatment supplies. Parental involvement reinforces messages at home, ensuring consistent monitoring and adherence to treatment schedules.

Personal Hygiene Practices

Effective control of head‑lice infestations relies heavily on strict personal hygiene routines. Clean hair and scalp reduce the likelihood of lice survival and limit opportunities for re‑infestation. Regular washing, thorough drying, and diligent care of personal items create an environment hostile to the parasite.

Practical hygiene measures include:

Daily shampooing with a regular or medicated formula, followed by thorough rinsing and complete drying of the scalp.
Frequent combing with a fine‑toothed lice comb to remove nits and adult insects after each wash.
Routine laundering of bedding, hats, scarves, and hair accessories in hot water (minimum 130 °F/54 °C) and drying on high heat.
Immediate cleaning of hairbrushes, combs, and hair‑care tools by soaking in hot, soapy water for at least 10 minutes.
Avoiding head‑to‑head contact and sharing personal items such as hair ties, helmets, or earbuds.
Periodic vacuuming of upholstered furniture and car seats to eliminate detached lice or eggs.

Consistent application of these practices, combined with any prescribed topical treatments, accelerates eradication and prevents recurrence.