Where are lice located on the human body?

Understanding Lice Infestations

Types of Human Lice

Head Lice («Pediculus humanus capitis»)

Head lice (Pediculus humanus capitis) inhabit the scalp and hair of humans. Adult insects cling to hair shafts with claws that fit the diameter of a single strand. They position themselves close to the skin surface to access blood from the scalp’s capillaries.

Typical colonization sites include:

The nape of the neck, where hair is dense and less frequently brushed.
The region behind the ears, offering warmth and shelter.
The crown and frontal hairline, especially in children with short hair.

Females embed eggs (nits) within the hair cuticle, usually within a half‑centimetre of the scalp. This proximity ensures optimal temperature for embryonic development and immediate access to the host upon hatching. Nymphs emerge and remain on the hair shaft, migrating to the same preferred regions as adults.

The concentration of lice is highest where hair is thick, the skin is warm, and mechanical disturbance (brushing, combing) is minimal. Effective detection and control focus on these areas.

Body Lice («Pediculus humanus corporis»)

Body lice, scientifically known as Pediculus humanus corporis, are obligate blood‑feeding ectoparasites that differ from head lice by inhabiting clothing rather than hair. Adult lice and nymphs remain on the surface of garments, moving to the skin only to feed.

Typical body sites where lice are encountered include:

Waistband and belt area
Groin and inner thigh folds
Axillary (underarm) region
Buttocks and perianal region
Areas where clothing is tight or seams are present

Females deposit eggs (nits) on fabric fibers, especially in seams and folds. Nits hatch within 7–10 days; emerging nymphs migrate to the skin surface to take a blood meal before returning to the clothing. The feeding process lasts a few minutes and may cause itching, erythema, or secondary infection if the host scratches.

Infestations arise primarily in conditions where clothing is worn continuously without regular laundering, such as in shelters, prisons, or among individuals lacking access to clean garments. Effective control requires washing infested clothing at ≥ 60 °C, drying on high heat, and maintaining personal hygiene to interrupt the lice life cycle.

Pubic Lice («Pthirus pubis»)

Pubic lice, scientifically known as Pthirus pubis, are obligate ectoparasites that inhabit the human body’s coarse hair regions. Their primary habitat is the pubic area, where they attach to terminal hair shafts and feed on blood.

Typical locations include:

Pubic hair (most common)
Axillary hair
Chest and abdominal hair
Facial hair (beard, mustache)
Eyebrows and eyelashes
Occasionally, scalp hair in heavily infested individuals

Preference for these sites derives from the combination of appropriate hair diameter, warmth, and moisture, which facilitate attachment and egg laying. The lice insert their claws into the hair shaft, creating a secure foothold.

Transmission occurs through direct skin‑to‑skin contact, most often during sexual activity, but also via sharing contaminated clothing, towels, or bedding. The insects cannot survive more than 24–48 hours off a host.

Clinical manifestations consist of intense pruritus, visible adult lice or translucent nits attached to hair shafts, and bluish maculae (fecal spots) near the skin surface. Diagnosis relies on visual examination of the affected hair.

Effective management includes topical pediculicides (e.g., permethrin 1 % or pyrethrins with piperonyl butoxide), thorough washing of clothing and bedding at ≥60 °C, and removal of nits with fine‑toothed combs. Follow‑up inspection after 7–10 days confirms eradication.

Specific Locations of Lice Infestation

Head Lice Infestation Areas

Scalp and Hair Shafts

Head lice (Pediculus humanus capitis) inhabit the scalp and the surrounding hair shafts. Adult insects cling to the hair shaft near the scalp, where temperature and humidity support their metabolism. They insert their mouthparts into the skin at the base of the hair follicle to feed on blood.

Typical infestation zones include:

The crown of the head, where hair density is greatest.
The occipital region, especially the area behind the ears.
The nape of the neck, where hair meets the skin.
The hair shaft itself, where nits are cemented within 1 cm of the scalp.

Nits (lice eggs) are firmly attached to the hair shaft, usually within a few millimeters of the scalp surface. The proximity to the skin ensures that newly hatched nymphs can quickly reach a feeding site. The combination of scalp warmth, moisture, and the hair’s structural support creates an optimal environment for the entire life cycle of the parasite.

Behind the Ears

Head lice (Pediculus humanus capitis) concentrate in the area behind the ears because the skin there is warm, moist, and less exposed to sunlight. The temperature and humidity promote egg (nits) attachment and nymph development, while hair density provides a secure grip for the insects.

Key factors that make the region behind the ears a preferred habitat:

Skin temperature averaging 33‑35 °C, optimal for lice metabolism.
Relative humidity of 50‑70 %, which prevents desiccation of eggs.
Thick hair covering that shelters lice from mechanical removal.
Limited airflow, reducing the chance of dislodgement.

Inspection of this zone is essential during screening. Look for live lice moving along hair shafts and for nits cemented within 1 mm of the scalp. Use a fine-toothed comb to separate hair and expose hidden insects.

Effective control measures focus on this area:

Apply a recommended pediculicide directly to the scalp and behind the ears, following product instructions.
Comb the hair with a nit comb for at least 10 minutes, covering the region behind the ears repeatedly.
Wash clothing, bedding, and personal items at 60 °C or seal them in a plastic bag for two weeks to eliminate detached lice.

Regular monitoring of the behind‑ear area after treatment reduces the risk of recurrence and confirms eradication.

Nape of the Neck

The human head louse (Pediculus humanus capitis) prefers warm, protected areas where hair density is high. The nape of the neck offers an optimal combination of temperature, humidity, and limited exposure to sunlight, making it a frequent site for infestation.

Hair at the nape forms a dense canopy that traps eggs (nits) and adult lice. The region’s reduced airflow compared with the scalp slows desiccation, allowing lice to survive longer. Additionally, the nape is less accessible for routine grooming, which delays detection and removal.

Key characteristics of the nape that support lice colonization:

Thick, overlapping hair shafts create a secure substrate for attachment.
Skin temperature averages 33‑35 °C, within the optimal range for lice metabolism.
Relative darkness limits ultraviolet exposure, which can be lethal to the insects.
Limited friction from daily combing reduces mechanical disturbance.

Effective control measures target the nape directly:

Apply a topical pediculicide to the entire hair length, ensuring thorough coverage of the posterior neck region.
Use a fine-toothed comb to remove nits from the hair at the nape, working from the scalp outward.
Wash bedding and clothing in hot water (≥60 °C) to eliminate displaced lice and eggs.

Monitoring the nape during inspections increases early detection, reducing the likelihood of widespread infestation across the scalp.

Body Lice Infestation Areas

Clothing Seams

Clothing seams provide a sheltered environment where lice can survive and reproduce. The tight stitching creates narrow pockets that retain heat and moisture, conditions favorable for both adult insects and their eggs. Head lice, which primarily inhabit the scalp, may crawl onto shirt collars and the inner edges of sleeves, where seams offer protection from frequent brushing. Body lice, which live on clothing rather than the skin, deposit nits directly into seam cavities; the larvae feed on the host’s blood when the garment is worn. Pubic lice occasionally occupy seams of tight undergarments, exploiting the same micro‑climate.

Key points about seam involvement:

Seams on collars, cuffs, and waistbands are most frequently infested because they remain in constant contact with skin.
Double‑stitched or reinforced seams retain more debris, increasing the likelihood of egg attachment.
Synthetic fabrics with smooth seams may reduce lice adherence compared to cotton or wool, which hold more static charge.

Effective management requires:

Removing and laundering all garments at temperatures above 130 °F (54 °C) to kill lice and nits within seams.
Inspecting seam interiors with a fine‑toothed comb or magnifying lens after washing.
Using a garment steamer to penetrate seam folds, ensuring complete eradication.

Understanding the role of clothing seams clarifies why lice are not confined solely to the scalp or body hair; they exploit any protected niche on the person’s attire.

Skin Folds

Lice are obligate ectoparasites that require close contact with human skin or hair for survival. While head lice (Pediculus humanus capitis) remain confined to the scalp, body lice (Pediculus humanus corporis) exploit areas where skin folds create sheltered microenvironments. These folds retain warmth and moisture, conditions that facilitate egg laying and nymph development.

Typical locations include:

Axillary (underarm) creases, where sweat and friction provide a humid niche.
Inguinal region and groin folds, offering protection from clothing abrasion.
Interdigital spaces of the hands and feet, especially in individuals with excessive sweating.
Perianal skin folds, where moisture accumulates.
Neck folds, particularly in individuals with short hair or high collar clothing.

Body lice often migrate to these sites after emerging from eggs laid in the seams of contaminated clothing. The insects attach their claws to the skin surface, feeding on blood several times a day. Regular inspection of skin folds, combined with proper hygiene and laundering of garments, reduces infestation risk.

Hair on the Body

Lice infestations are confined to areas where human hair provides a substrate for attachment and egg deposition. The primary species, Pediculus humanus capitis (head lice), inhabit the scalp, clinging to the shafts of scalp hair and laying nits close to the scalp surface. Body lice, Pediculus humanus corporis, occupy coarse body hair, especially in regions where clothing contacts the skin.

Typical hair sites that support lice include:

Scalp hair
Facial hair (beard, moustache)
Axillary (under‑arm) hair
Pubic hair
Chest and abdominal hair
Leg and arm hair, when sufficiently dense

Lice are absent from hair‑less skin, mucous membranes, and areas where hair is extremely fine or sparse. Their survival depends on the presence of viable hair for feeding, movement, and reproduction.

Pubic Lice Infestation Areas

Pubic Hair

Pubic hair provides a warm, protected niche that supports the life cycle of the crab‑type louse (Pthirus pubis). The hair shafts create a stable microenvironment, shielding the insects from temperature fluctuations and facilitating attachment of their claws. The dense, coarse texture of genital hair also allows the lice to move easily and lay eggs (nits) close to the skin surface, where they remain attached to the hair shaft until hatching.

Key characteristics of this location include:

High humidity and warmth, which accelerate nymph development.
Limited grooming in the genital region, reducing mechanical removal of parasites.
Proximity to skin folds, offering easy access to blood meals.

Detection typically involves visual identification of live insects or translucent nits attached near the base of the hair. Effective management consists of:

Topical pediculicides (e.g., permethrin 1% or pyrethrin‑based products) applied according to package directions.
Manual removal of nits with a fine‑toothed comb after treatment.
Washing of clothing, bedding, and towels at temperatures above 50 °C or sealing them in plastic bags for two weeks to eliminate residual parasites.

Understanding the biology of pubic hair as a habitat clarifies why this area is the primary site for crab lice infestation on the human body.

Eyelashes and Eyebrows (in children)

Lice that infest the head often extend their grip to the fine hairs surrounding the eyes. In children, the most common species, Pediculus humanus capitis, can lay eggs on eyelashes and eyebrows because these hairs provide a sheltered environment similar to scalp hair. The proximity to the scalp facilitates transfer of nits during daily activities such as brushing or head‑to‑head contact.

Typical indicators of infestation on the peri‑ocular region include:

Small, white or brown specks attached to the base of lashes or brows (nits)
Live insects moving slowly along the hair shafts
Persistent itching or redness around the eyes and eyebrows
Secondary irritation from scratching, which may lead to crusted lesions

Diagnosis relies on visual inspection with a magnifying device. Removal of visible nits and live lice is performed with fine‑toothed combs designed for delicate facial hair. Topical pediculicides approved for pediatric use, such as permethrin 1 % lotion, may be applied to the affected area following the manufacturer’s instructions, ensuring avoidance of the ocular surface. Re‑treatment after seven days eliminates newly hatched lice that escaped the initial application.

Prevention focuses on minimizing direct head contact among children, regular cleaning of personal items (hats, scarves, hairbrushes), and routine checks of eyelashes and eyebrows during school health screenings. Early identification and prompt treatment reduce the risk of spread to other children and prevent secondary skin infections.

Other Coarse Body Hair

Lice are obligate ectoparasites that require dense, relatively short hair for attachment, feeding, and reproduction. While the scalp provides the optimal environment, other thick hair regions can also support infestations, though less commonly.

The following coarse body hair types are occasionally colonized:

Beards and mustaches: facial hair offers sufficient length for nits to be cemented, especially in men with dense growth.
Chest and abdominal hair: moderate density allows adult lice to move, but limited surface area reduces population size.
Pubic hair: known as “crabs,” this region supports a specialized species that prefers the coarse, curly texture.
Armpit hair: occasional reports of temporary colonization, typically after contact with infested scalp hair.

Hair regions that lack sufficient length or density—such as eyebrows, eyelashes, and fine body hair—do not provide a viable habitat for lice. The presence of lice on these coarse hairs depends on factors including hair thickness, moisture, and temperature, which together create a microenvironment conducive to survival.

Factors Influencing Lice Location

Environmental Conditions

Lice thrive where the external environment of the host meets their physiological requirements. The scalp and body hair provide a sheltered microclimate that maintains a temperature close to 33 °C and relative humidity between 70 % and 90 %. These parameters support egg incubation and adult metabolism, limiting desiccation and heat stress.

Key environmental factors influencing lice distribution on a person include:

Temperature stability – consistent warmth prevents cold‑induced mortality.
Humidity level – high moisture reduces water loss through the cuticle.
Hair density and length – thicker, longer hair creates a thicker insulating layer.
Sebum production – skin oils supply nutrients and affect surface moisture.
Airflow restriction – limited ventilation preserves the microclimate within the hair shaft.

Variations in these conditions shift lice populations toward areas that best preserve the required thermal and hygroscopic environment, typically the scalp, chest hair, and pubic region where hair and sweat combine to create optimal habitats.

Hair Type and Density

Lice survive by anchoring their claws to individual hair shafts, so the characteristics of a person’s hair directly affect where the insects can be found.

Hair type influences the ease with which lice can grasp and move. Straight or slightly wavy hair provides a smooth surface that allows rapid traversal, while tightly curled or coiled hair creates more bends and loops, offering additional niches for eggs (nits) to remain concealed from removal attempts.

Hair density determines the number of available attachment points. High‑density regions—typically the scalp, eyebrows, eyelashes, and facial hair—present the greatest concentration of viable sites. Low‑density areas, such as the neck or arms, support fewer lice because the reduced number of shafts limits both feeding and oviposition opportunities.

Key points:

Straight/wavy hair: facilitates swift movement; eggs often placed near the scalp where hair is longest.
Curly/coily hair: creates tighter spaces; nits may be hidden within curls, making detection harder.
High density (≥150 hairs/cm²): supports larger colonies; most infestations concentrate on the scalp and facial hair.
Low density (<100 hairs/cm²): sustains smaller populations; occasional lice may be found on body hair in warm, humid conditions.

Understanding the interplay between hair morphology and density clarifies why lice predominantly inhabit the scalp, eyebrows, eyelashes, and other densely haired regions, while their presence on sparsely haired skin remains uncommon.

Host Hygiene Practices

Effective personal hygiene limits the habitats where lice can survive on a human host. Regular washing with soap or shampoo removes the organic debris that nits and adult insects require for attachment and feeding. Daily shampooing of the scalp, combined with thorough combing, disrupts the life cycle of head lice and reduces the likelihood of infestation in hair shafts.

Body lice depend on clothing and prolonged skin contact with soiled garments. Frequent laundering of underwear, socks, and outerwear at temperatures above 60 °C eliminates larvae and eggs. Rotating clean clothing, storing worn items in sealed plastic bags until washed, and maintaining dry conditions prevent the warm, moist environment favored by body lice.

Pediculosis on the pubic region, caused by crab lice, is mitigated by routine genital hygiene. Gentle cleansing with mild antiseptic solutions, followed by drying, removes the moisture required for survival. Avoiding shared towels, bedding, and personal items removes vectors that transmit the parasites.

Key hygiene actions:

Shampoo scalp daily; use fine-toothed comb after washing.
Wash clothing, bedding, and towels in hot water; dry on high heat.
Change undergarments and socks at least once daily.
Clean and dry genital area with mild antiseptic; avoid sharing personal items.
Inspect hair and body regularly for live insects or nits; treat promptly if detected.