What is the disease caused by head lice called?

The Scientific Term for Head Lice Infestation

What Are Head Lice?

Head lice (Pediculus humanus capitis) are obligate ectoparasites that live on the human scalp, feeding on blood several times a day. Adult insects measure about 2–3 mm, are tan to gray, and lay eggs (nits) that adhere firmly to hair shafts near the scalp. The life cycle, from egg to adult, spans approximately 7–10 days, allowing rapid population growth under favorable conditions.

Typical manifestations include:

Persistent itching caused by an allergic reaction to saliva injected during feeding;
Visible live lice or translucent nits attached to hair;
Irritation or redness of the scalp, sometimes accompanied by secondary bacterial infection.

The medical condition resulting from infestation is termed pediculosis capitis. Diagnosis relies on direct visual inspection of the scalp and hair, using a fine-toothed comb to separate lice and nits. Absence of systemic symptoms distinguishes this disorder from other dermatologic or infectious diseases.

Management strategies consist of:

Topical pediculicides (e.g., permethrin 1 % or pyrethrin‑based formulations) applied according to product instructions;
Mechanical removal of nits with a specialized comb, repeated over several days to capture newly hatched lice;
Environmental decontamination, including laundering of bedding, clothing, and personal items at temperatures ≥ 60 °C or sealing them in plastic bags for two weeks.

Effective control requires adherence to treatment protocols, thorough combing, and monitoring for reinfestation over a 2–3‑week period.

The Life Cycle of Head Lice

Head lice (Pediculus humanus capitis) complete their development on a human scalp in three distinct stages. The female deposits eggs, called nits, near the hair shaft base. Each nit is firmly attached with a cement-like substance and hatches after 7–10 days at optimal temperature (≈30 °C).

Nymph stage: Newly emerged nymphs resemble miniature adults but lack full reproductive capacity. They undergo three molts, each lasting approximately 2–3 days, during which they feed on blood and increase in size.
Adult stage: Fully mature lice appear after about 9–12 days from hatching. Adults measure 2–4 mm, survive up to 30 days on a host, and females lay 5–10 eggs per day, continuing the cycle.

The entire life cycle, from egg to egg-laying adult, spans roughly 21 days under favorable conditions. Overcrowding, insufficient blood supply, or harsh environmental changes can shorten adult longevity, but the cycle persists as long as the host provides a warm, protected environment for feeding and reproduction.

How Head Lice Spread

Pediculosis capitis, the medical term for the infestation caused by head lice, spreads primarily through direct head‑to‑head contact. The insects cannot jump or fly; they crawl, making physical proximity the most efficient transmission route.

Close personal contact, especially among children in schools, daycare centers, and sports teams.
Sharing personal items such as combs, brushes, hats, hair accessories, or headphones.
Contact with contaminated bedding, pillows, blankets, or clothing that has recently housed an infested individual.
Use of infested hair‑care tools in salons or barbershops without proper disinfection.

Risk intensifies in crowded environments where regular head inspections are uncommon. Frequent laundering of personal textiles and avoiding the exchange of hair‑related objects reduce transmission probability. Early detection and prompt treatment interrupt the life cycle and limit further spread.

Symptoms and Diagnosis

Common Signs of Head Lice

Head lice infestation, medically known as pediculosis capitis, produces several recognizable clinical manifestations. Itching of the scalp is the most frequent complaint, caused by the allergic reaction to lice saliva. Persistent scratching may lead to erythema, excoriations, or secondary bacterial infection.

Visible indicators include:

Live adult lice or nymphs moving on the scalp or hair shafts.
Nits securely attached to the hair shaft within a half‑inch of the scalp; they appear as tiny, oval, white or yellowish shells.
Empty nits (shells without embryos) that remain attached after the lice have hatched.
A tickling or crawling sensation, especially when hair is brushed or combed.

Additional signs may involve localized swelling of the scalp skin, crusted lesions from chronic irritation, and occasional hair loss in severe cases. Prompt identification of these symptoms facilitates early treatment and prevents spread.

Visual Inspection for Lice and Nits

Visual inspection remains the primary method for confirming an infestation of head‑lice and detecting their eggs, known as nits. The examiner should separate the hair from the scalp using a fine‑tooth comb or a dedicated lice detection comb, working in sections of 2–3 cm. Each pass must be examined under adequate lighting, preferably with a magnifying lens, to identify live lice, dead specimens, or viable nits attached to hair shafts within ¼ inch of the scalp.

Key indicators observable during inspection:

Live lice: brown‑gray, mobile insects approximately 2–3 mm in length; movement may be detected when the comb is lifted.
Viable nits: oval, white or yellowish bodies firmly cemented to the hair shaft; the presence of a clear, curved attachment near the scalp suggests recent oviposition.
Empty nits: translucent shells that have detached from the hair shaft; their presence indicates a past infestation but does not confirm current activity.
Scalp irritation: redness, scratching marks, or localized inflammation, often accompanying active infestation.

Procedural steps for a thorough visual examination:

Position the subject in a well‑lit area; use a handheld lamp or natural daylight.
Part the hair into small sections, securing each with clips if necessary.
Run the lice comb through each section from scalp outward, pulling the comb slowly to avoid dislodging specimens.
After each pass, wipe the comb on a white tissue or disposable surface to reveal captured lice or nits.
Record findings: note the number of live lice, viable nits, and their distribution on the scalp.
Repeat the process after 7–10 days to verify treatment efficacy, as newly hatched lice become detectable only after this interval.

Accurate visual detection enables prompt diagnosis of the condition caused by head‑lice infestation and guides appropriate therapeutic measures.

When to Seek Medical Advice

Head lice infestation, medically known as pediculosis capitis, often resolves with over‑the‑counter treatments, but certain circumstances require professional evaluation.

Seek medical attention if any of the following occur:

Persistent itching or rash lasting more than two weeks despite appropriate topical therapy.
Visible live lice or nymphs after two complete treatment cycles.
Secondary bacterial infection signs, such as redness, swelling, pus, or fever.
Allergic reactions to lice‑control products, including rash, swelling, or breathing difficulty.
Infestation in infants younger than six months or in individuals with compromised immune systems.
Uncertainty about diagnosis, especially when other scalp conditions (e.g., eczema, psoriasis) may mimic lice symptoms.

Prompt consultation ensures accurate diagnosis, appropriate prescription medication, and guidance on preventing reinfestation.

Treatment Options

Over-the-Counter Remedies

Head lice infestation, medically known as pediculosis capitis, is treated with a range of over‑the‑counter products designed to eliminate the parasites and their eggs.

Common OTC options include:

Permethrin 1 % lotion or shampoo – synthetic pyrethroid that paralyzes lice; applied to dry hair, left for 10 minutes, then rinsed.
Pyrethrin‑based sprays or creams – natural extracts combined with piperonyl butoxide; require a second treatment after 7–10 days to target newly hatched nymphs.
Dimethicone (silicone) lotion – suffocates lice without neurotoxic action; safe for children and pregnant users; left on hair for 8–10 hours before washing.
Benzyl alcohol lotion – kills lice by asphyxiation; requires a repeat application after 7 days; not suitable for infants under 6 months.
Spinosad 0.9 % suspension – insecticide that disrupts nerve function; applied for 10 minutes, then rinsed; effective against permethrin‑resistant strains.
Lice combs (fine‑toothed metal or plastic) – mechanical removal of live lice and nits; used after chemical treatment or as a standalone method for mild cases.

Effective treatment typically follows a two‑step protocol: apply the chosen product according to label instructions, then repeat after 7–10 days to eradicate any surviving eggs. Concurrent use of a comb to remove nits reduces reinfestation risk. All products should be stored out of reach of children and used only as directed.

Prescription Medications

Head lice infestation, medically known as pediculosis capitis, is treated with prescription‑only medications when over‑the‑counter options fail or resistance is suspected. These agents are formulated to kill both adult lice and their eggs, reducing the risk of recurrence.

Permethrin 5 % lotion – a synthetic pyrethroid applied to dry hair for ten minutes, then rinsed. Requires a second application 7–10 days later to eradicate newly hatched lice.
Malathion 0.5 % lotion – an organophosphate insecticide left on the scalp for 8–12 hours before washing. Effective against permethrin‑resistant populations; contraindicated in infants under 6 months.
Spinosad 0.9 % suspension – a bacterial‑derived compound applied for 10 minutes, then rinsed. Single‑dose regimen; minimal irritation reported.
Benzyl alcohol 5 % lotion – a pediculicidal agent that suffocates lice; applied for 10 minutes, repeated after 7 days. Not approved for children under 2 years.
Ivermectin 0.5 % lotion – a macrocyclic lactone applied for 10 minutes, then washed off; a second treatment may be needed after one week.

Prescription treatments must be prescribed based on patient age, allergy history, and local resistance patterns. Proper application instructions are critical to achieve therapeutic success and prevent adverse reactions. Monitoring for treatment failure guides the choice of alternative agents or combination therapy.

Home Remedies and Their Efficacy

Pediculosis capitis, commonly known as head‑lice infestation, can be managed with several over‑the‑counter and household treatments. Evidence varies, but certain home remedies demonstrate measurable effectiveness when applied correctly.

Tea tree oil (5‑10 % solution) – Studies show a reduction in live lice after a single application, likely due to its insecticidal constituents. Re‑treatment after 7 days improves eradication rates.
Neem oil (10‑20 % concentration) – Laboratory tests confirm mortality of both lice and nits; clinical reports suggest success when combined with a thorough combing regimen.
Apple‑cider vinegar (undiluted) – Acidic environment weakens lice grip on hair shafts, facilitating removal with a fine‑toothed nit comb. Results are inconsistent; supplemental chemical pediculicides increase overall efficacy.
Mayonnaise (full‑fat, applied for 2 hours) – Occlusive action suffocates lice; limited trials report modest lice loss, but persistence of nits remains a concern.
Lemon juice (fresh, applied for 30 minutes) – Low pH disrupts lice exoskeletons; effectiveness comparable to vinegar, requiring diligent combing to achieve acceptable clearance.

Key factors influencing success include concentration, exposure time, and thorough mechanical removal of nits with a nit comb. Single‑application protocols rarely achieve complete eradication; a repeat treatment after 7–10 days is standard to target newly hatched lice. Combining a proven home remedy with a mechanical combing step yields the highest clearance rates, while reliance on any single remedy without follow‑up often results in residual infestation.

Prevention and Control

Hygiene Practices

Pediculosis capitis, a common infestation of the scalp, is controlled primarily through rigorous hygiene measures. Effective practices include:

Regular combing with a fine‑tooth lice comb on wet, conditioned hair to mechanically remove lice and nits.
Frequent washing of personal items—hats, scarves, hairbrushes, and pillowcases—in hot water (≥60 °C) or by using a dryer on high heat.
Immediate laundering of clothing worn during close contact, followed by drying on a hot setting.
Avoidance of sharing personal headgear or hair accessories; store such items in sealed containers when not in use.
Application of over‑the‑counter pediculicides according to label instructions, combined with a repeat treatment after 7–10 days to target newly hatched lice.
Thorough cleaning of living spaces: vacuum carpets, upholstery, and vehicle seats; discard or isolate infested bedding for at least 48 hours.

Consistent implementation of these steps reduces transmission risk and accelerates eradication of the scalp infestation.

Screening and Early Detection

Head‑lice infestation, medically termed pediculosis capitis, commonly affects school‑age children and can spread rapidly in communal settings. Early identification limits transmission and prevents secondary skin irritation.

Screening programs target environments where close contact occurs: elementary schools, daycare centers, and family households with a recent case. Routine checks reduce outbreak magnitude and decrease the need for extensive treatment.

Effective early detection relies on direct observation and standardized tools:

Visual inspection of the scalp and hairline for live lice or viable nits within 1 cm of the scalp.
Use of a fine‑toothed lice comb on wet hair, performed at least once weekly during high‑risk periods.
Documentation of findings in a centralized log to track prevalence and trigger timely interventions.

Guidelines advise that trained personnel conduct examinations before the start of the school day, repeat assessments after a two‑week interval, and initiate treatment promptly upon confirmation. Communication with caregivers includes instructions for home‑based verification and simultaneous treatment of close contacts.

Managing Infestations in Communities

Pediculosis, the medical term for an infestation of head lice, spreads rapidly in densely populated settings such as schools, daycare centers, and refugee camps. Effective community management requires coordinated actions that address detection, treatment, and prevention simultaneously.

Prompt identification relies on routine scalp inspections conducted by trained personnel. Visual confirmation of live lice or viable nits should trigger immediate reporting to health authorities. Documentation of cases enables tracking of outbreak magnitude and informs resource allocation.

Treatment protocols consist of two complementary steps. First, apply a proven pediculicide—either a topical insecticide or a silicone‑based product—according to manufacturer guidelines. Second, execute a thorough mechanical removal process, combing wet hair with a fine‑toothed lice comb for at least ten minutes per individual. Re‑treatment after seven days eliminates hatching nits.

Preventive measures reduce recurrence. Implement the following practices:

Educate caregivers and students on personal hygiene and the importance of avoiding head-to-head contact.
Disinfect personal items (combs, hats, pillowcases) using hot water (≥ 130 °F) or a suitable disinfectant.
Establish a “no‑nit” policy that permits re‑entry only after confirmation of successful treatment.
Schedule periodic community screenings during peak transmission seasons.

Collaboration with local healthcare providers ensures access to affordable medication and professional guidance. Data collected from each outbreak should be analyzed to refine intervention strategies, aiming to minimize the public health burden of head‑lice infestations.

Complications and Misconceptions

Potential Health Issues from Infestation

Head lice infestation, medically known as pediculosis capitis, can lead to several health complications beyond the immediate discomfort of itching. The primary concerns include:

Dermatological reactions: Repeated scratching may cause erythema, excoriations, and secondary bacterial infections such as impetigo.
Allergic responses: Some individuals develop hypersensitivity to lice saliva, resulting in pronounced erythema, swelling, and intense pruritus.
Psychological impact: Persistent infestation can cause anxiety, embarrassment, and social stigma, especially among school‑aged children.
Transmission of pathogens: Although rare, head lice can act as vectors for bacterial agents like Staphylococcus aureus and Streptococcus pyogenes, facilitating skin infections.

Effective management requires prompt removal of lice and nits, thorough cleaning of personal items, and monitoring for signs of infection. Early intervention reduces the risk of complications and limits spread within communities.

Debunking Common Myths About Lice

Head lice infestations, medically termed pediculosis capitis, are often misunderstood. The condition does not indicate poor hygiene; lice thrive in clean environments as well as unclean ones. Transmission occurs through direct head-to-head contact, not through pets or contaminated surfaces, because lice cannot survive long off a human host.

Common misconceptions:

Myth: Over‑the‑counter shampoos eradicate lice.
Fact: Most shampoos lack the insecticidal concentration required to kill nits; prescription‑strength treatments or proper combing are necessary for complete eradication.
Myth: Lice spread diseases.
Fact: Pediculosis capitis is a nuisance infestation; it does not transmit pathogens or cause systemic illness.
Myth: Re‑infestation means treatment failure.
Fact: Re‑infestation often results from untreated contacts or missed nits; thorough examination of all close contacts and repeated nit removal prevent recurrence.
Myth: Home remedies such as mayonnaise or petroleum jelly cure lice.
Fact: These substances suffocate adult lice temporarily but do not affect nits; they provide no reliable cure.

Effective management combines a proven pediculicide, meticulous nit combing, and simultaneous treatment of all individuals exposed to the infestation. Regular follow‑up checks at 7‑ and 14‑day intervals confirm elimination and reduce the likelihood of resurgence.

Impact on Mental and Emotional Well-being

Pediculosis capitis, the medical term for head‑lice infestation, affects millions of children and adults worldwide. The condition is diagnosed by the presence of live lice or viable nits attached to scalp hair.

The infestation triggers anxiety about personal hygiene and fear of contagion. Affected individuals often experience heightened self‑consciousness, leading to avoidance of social interactions and public spaces.

Emotional responses include embarrassment, irritability, and diminished self‑esteem. Persistent itching disrupts sleep, amplifying fatigue and mood instability. Families may encounter frustration and tension as they manage treatment protocols and prevent re‑infestation.

Key mental and emotional consequences:

Persistent worry about stigma and transmission
Reduced confidence in personal appearance
Increased stress due to treatment demands and school or work absenteeism
Strained relationships within households and peer groups

Addressing these effects requires prompt medical treatment, clear communication about the non‑contagious nature of symptoms after eradication, and supportive counseling to mitigate psychological distress.