What is the medical term for lice?

Understanding Pediculosis

Types of Pediculosis

Pediculosis, the clinical designation for infestation by lice, manifests in several distinct forms that correspond to the preferred anatomical sites of the parasite.

Head pediculosis (Pediculus humanus capitis) – infestation of the scalp and hair shafts; most common in school‑age children. Nits are attached to hair shafts near the scalp, and adult lice move quickly across the scalp surface.
Body pediculosis (Pediculus humanus corporis) – infestation of clothing and skin folds; the organism lives in seams of garments and feeds intermittently on the host. Transmission often follows poor hygiene or crowded living conditions.
Pubic pediculosis (Pthirus pubis) – infestation of the genital region, perianal area, and occasionally facial hair. The parasite is shorter and broader than head or body lice, and its eggs adhere to coarse hair.
Animal‑associated pediculosis – includes species such as Felicola spp. (cat lice) and Linognathus spp. (dog lice). These infestations affect companion animals and may occasionally transfer to humans through close contact.

Each type shares the characteristic life cycle of egg, nymph, and adult stages, but differs in habitat, morphology, and epidemiology. Accurate identification guides appropriate treatment, which typically involves topical pediculicides and removal of nits, complemented by environmental decontamination for body lice.

Causes and Transmission

Pediculosis, the clinical term for an infestation of lice, results from three primary sources. First, direct skin‑to‑skin contact with an infested individual transfers adult insects and nymphs. Second, sharing personal items—combs, hats, scarves, bedding, or clothing—provides a conduit for lice eggs (nits) and newly hatched nymphs. Third, environments with high density of people, such as schools, camps, or shelters, increase exposure risk through frequent close interactions.

Transmission proceeds through the following mechanisms:

Adult lice crawl onto a new host during brief contact; they cannot jump or fly, so movement relies on physical transfer.
Nits attached to hair shafts survive for up to ten days off the host; they hatch when placed on a suitable scalp, initiating a new infestation.
Re‑infestation occurs when previously treated individuals acquire lice again from untreated contacts or contaminated items.

Effective control requires eliminating both live insects and viable eggs, and interrupting the pathways of spread.

Diagnosis and Symptoms

Common Symptoms of Lice Infestation

Lice infestation, medically termed pediculosis, presents with a predictable set of clinical signs. The most reliable indicator is persistent itching of the scalp, caused by an allergic reaction to saliva injected during feeding. Visible nits—tiny, oval, translucent eggs—adhere firmly to hair shafts within a quarter‑inch of the scalp. Adult lice, measuring 2–4 mm, may be observed moving quickly across the scalp or clinging to clothing. Secondary skin lesions appear where scratching has damaged the epidermis, leading to erythema, excoriations, and occasional crust formation. In severe cases, bacterial superinfection can develop, manifested by localized swelling, warmth, and purulent discharge.

Key symptoms include:

Intense pruritus, especially after periods of inactivity
Presence of live lice or empty shells on hair or garments
Nits attached to hair shafts close to the scalp
Red, irritated patches with scratch marks
Signs of infection such as pus, warmth, or swelling

Recognition of these findings enables prompt diagnosis and treatment, reducing the risk of complications and transmission.

Diagnostic Procedures

Pediculosis, the clinical designation for an infestation of lice, is confirmed through direct examination and laboratory techniques. The primary approach involves a systematic visual assessment of the scalp, hair, eyebrows, eyelashes, or body hair, searching for live insects and attached ova (nits). Examination should be performed under adequate lighting, using a fine-tooth comb to separate hair strands and reveal concealed specimens.

Additional diagnostic methods include:

Dermoscopy or a handheld magnifying device to identify nymphs, adult lice, and nits attached near the hair shaft base.
Microscopic analysis of collected nits after removal; hatchability testing distinguishes viable eggs from empty shells.
Wood’s lamp examination, occasionally employed to enhance visualization of fluorescing debris associated with heavy infestations.
Skin scraping for concurrent dermatoses when lesions coexist with lice, ensuring accurate differential diagnosis.

These procedures provide definitive evidence of infestation, guide appropriate therapeutic decisions, and facilitate monitoring of treatment efficacy.

Treatment Options for Pediculosis

Over-the-Counter Treatments

Pediculosis, the clinical term for an infestation of head lice, is commonly treated with products available without a prescription. These agents are formulated to kill live lice while minimizing irritation to the scalp.

Permethrin 1 % lotion – synthetic pyrethroid; applied to dry hair for 10 minutes, then rinsed; repeat after 7–10 days to eliminate newly hatched nymphs.
Pyrethrin‑piperonyl‑butoxide spray – natural extract combined with a synergist; short contact time (10 minutes) before washing; effective for mild infestations.
Dimethicone 4 % lotion – silicone‑based, suffocates lice; left on hair for 10 minutes, then combed and rinsed; low toxicity, suitable for children.
Malathion 0.5 % lotion – organophosphate; applied for 8–12 hours before shampooing; reserved for resistant cases due to potential skin irritation.
Benzyl alcohol 5 % lotion – non‑neurotoxic; applied for 10 minutes, then rinsed; kills lice but not eggs, requiring a second treatment after 7 days.
Ivermectin 0.5 % lotion – macrocyclic lactone; single 10‑minute application; effective against resistant strains, limited to older children and adults.

Correct use includes washing hair before application, following the product’s timing instructions precisely, and performing a thorough nit comb after treatment. A repeat dose is essential to address any eggs that survived the initial exposure. Resistance to pyrethrins and permethrin has increased, prompting clinicians to recommend dimethicone or ivermectin when treatment failure is observed. Safety profiles are favorable for most OTC options, though malathion and high‑concentration permethrin may provoke dermatitis in sensitive individuals.

Prescription Medications

The medical designation for an infestation of lice is pediculosis. Prescription‑only agents are reserved for cases where over‑the‑counter products fail or when resistance is documented. Clinicians select systemic or topical formulations based on severity, patient age, and comorbidities.

Effective prescription options include:

Ivermectin (oral or topical) – a macrocyclic lactone that disrupts nerve transmission in lice; dosage adjusted for weight; contraindicated in pregnancy.
Malathion 0.5 % lotion – organophosphate that inhibits acetylcholinesterase; applied to dry hair for 8–12 hours; not recommended for children under 2 years.
Benzyl alcohol 5 % lotion – neurotoxic to lice, safe for infants older than 6 months; requires repeat application after 7 days.
Spinosad 0.9 % suspension – derived from bacterial fermentation, effective after a single 10‑minute exposure; limited data for use in children under 12 years.

Prescription regimens typically involve:

Confirming diagnosis through visual inspection or microscopy.
Selecting an agent with proven efficacy against local resistance patterns.
Providing clear instructions on application duration, repeat dosing, and environmental decontamination.
Monitoring for adverse reactions, especially neurotoxicity or skin irritation.

Systemic ivermectin may be preferred for extensive scalp involvement or when topical agents are impractical. All prescriptions require patient education on proper use to minimize re‑infestation and resistance development.

Home Remedies and Prevention

The clinical designation for a lice infestation is pediculosis, with head‑specific cases referred to as pediculosis capitis. Effective management often begins with readily available home measures.

Wet combing: Apply a generous amount of conditioner to damp hair, then run a fine‑tooth comb through sections from scalp to ends. Repeat every 2–3 days for two weeks.
Petroleum jelly: Coat hair and scalp with a thin layer, leave for several hours, then remove with a comb. This suffocates the insects.
Tea tree oil: Dilute a few drops in a carrier oil, apply to scalp, and leave for 30 minutes before rinsing. The oil’s insecticidal properties reduce live lice.
Apple cider vinegar rinse: Mix equal parts vinegar and water, pour over hair, and let sit for 5 minutes. The acidic environment loosens nits from the shaft.

Prevention relies on minimizing transmission opportunities.

Avoid sharing combs, brushes, hats, helmets, or hair accessories.
Wash bedding, pillowcases, and clothing used by the infested person in water ≥130 °F (54 °C) and dry on high heat.
Perform regular scalp inspections, especially in group settings such as schools or daycare.
Store personal items separately; keep hair tied back when in close‑contact environments.
Maintain clean grooming tools by soaking them in hot, soapy water for at least 10 minutes before reuse.

Combining these home interventions with diligent preventive habits reduces the likelihood of recurrence and limits spread within households and communities.