What do lice look like on a human head?

Understanding Head Lice

What Are Head Lice?

Size and Shape

Head lice (Pediculus humanus capitis) measure approximately 2–4 mm in length, comparable to a grain of rice. Their bodies are flattened laterally, allowing easy movement through hair shafts. Adult females tend toward the upper end of the size range, while males are slightly smaller.

The overall silhouette is oval when viewed from the side, with a broader anterior region housing the head and mouthparts. The posterior segment tapers, ending in a pair of short, claw‑like structures that grasp individual hair strands. Six legs, each ending in a single claw, are positioned symmetrically on the thorax and facilitate rapid locomotion.

Length: 2 mm (nymph) to 4 mm (adult)
Width: 0.8–1.0 mm across the thorax
Body shape: dorsoventrally flattened, oval profile
Head: rounded, equipped with chewing mouthparts
Legs: six, each with a single claw for hair attachment

Nymphs resemble adults in shape but are uniformly smaller, lacking the darker pigmentation seen in mature insects. All stages retain the same flattened, oval configuration that enables concealment within the hair.

Color and Transparency

Head lice are small, wing‑less insects about 2–4 mm long. Their exoskeleton exhibits a gray‑brown hue that ranges from light ash to darker coffee tones. Color intensity varies with age and feeding status; newly hatched nymphs appear paler, while mature adults develop a richer brown shade after blood meals.

The cuticle of lice is partially translucent. Light passes through the thin dorsal plates, making unfed individuals appear almost glassy. After ingesting blood, the abdomen expands and becomes more opaque, reducing the degree of transparency. In a dry scalp environment, the semi‑transparent quality allows lice to blend with hair shafts and skin, complicating visual detection.

Light gray‑brown (early nymphs) – high translucency
Medium brown (fed nymphs) – moderate translucency
Dark brown to black (fully fed adults) – low translucency

These color and transparency characteristics define the visual profile of lice on a human head.

Where to Find Lice on the Scalp

Hairline and Neck

Lice on the hairline and neck appear as tiny, flattened insects measuring 2–3 mm in length. Their bodies are tan to grayish‑brown, with a broader, broader posterior and a narrower head. The legs end in claw‑like tarsi that cling tightly to hair shafts, making movement along the fringe and lower scalp visible.

Nits (lice eggs) are often confused with dandruff but differ in size and attachment. They are oval, 0.8 mm long, and cemented at an angle to the hair shaft. At the hairline, nits are more likely to be found close to the scalp surface, while on the neck they sit lower on the shaft and may appear slightly more translucent.

Key visual cues for identification:

Body color: tan, gray‑brown, sometimes slightly reddish after feeding.
Shape: flat, oval, with a wider rear half.
Legs: six, short, ending in hooked claws.
Movement: rapid, up and down the hair shaft.
Nits: oval, firmly attached, angled toward the scalp; not easily dislodged by brushing.

Observing these characteristics directly on the hairline or neck allows reliable detection without microscopy.

Behind the Ears

Lice that inhabit the scalp are most often observed behind the ears, where hair density and warmth create an ideal environment. Adult head lice measure 2–4 mm in length, have a flattened, elongated body, and are typically gray‑brown to tan. Their six legs end in claw‑like tarsi that grasp hair shafts securely.

Key visual indicators behind the ears:

Body color: gray‑brown, sometimes with a slightly reddish hue after feeding.
Size: about the length of a grain of rice; nymphs are proportionally smaller.
Shape: laterally compressed, giving a “flattened” appearance.
Movement: slow, crawling; they do not jump.
Eggs (nits): oval, 0.8 mm long, firmly attached to hair close to the scalp; appear white or yellowish and are often mistaken for dandruff but cannot be brushed away easily.

Because the hair near the ear is short and lies close to the skin, nits are usually found within 1 cm of the scalp surface. The region also tends to retain moisture, making it easier to spot live insects during a thorough inspection. A magnifying lens or a fine‑toothed comb can reveal the characteristic oval nits and the mobile adult lice.

Effective detection relies on systematic examination of the hair strands behind each ear, looking for the described coloration, size, and attachment pattern. Identifying these signs promptly enables targeted treatment and prevents further spread across the scalp.

Other Common Areas

Lice are most visible on the scalp, but they also colonize additional regions where hair provides a habitat. Typical secondary sites include:

The hairline, especially at the forehead and nape, where hair density remains high.
The eyebrows and eyelashes; nits attach to the short hairs and may cause irritation.
The ears, particularly the outer rim and behind the ear, where hair is fine and sheltered.
The neck and upper shoulders, where hair may extend and create a warm microenvironment.
The beard or facial hair in males, which offers a comparable substrate for infestation.

These areas share common characteristics: presence of hair, limited exposure to sunlight, and a temperature conducive to lice development. Inspection should extend beyond the crown to detect early signs of infestation.

Distinguishing Lice Stages

Nits («Lice Eggs»)

Appearance and Attachment

Human head lice are tiny, wingless insects measuring 2–4 mm in length. The body is flattened laterally, facilitating movement through hair shafts. Color ranges from pale gray to brown, often appearing translucent after feeding. Each louse has a segmented abdomen, three pairs of legs ending in clawed tarsi that grasp individual hair strands, and a pair of antennae equipped with sensory pits. The head bears a small, rounded thorax and a dorsal suture visible as a faint line. Eyes are reduced to simple ocelli, and the mouthparts form a piercing‑sucking apparatus for blood extraction.

Attachment relies on the clawed legs, which lock onto hair cuticles at angles of 30–45 degrees, preventing dislodgement by brushing or washing. Lice position themselves close to the scalp, where warmth and blood supply are optimal. They lay eggs, called nits, firmly cemented to the hair shaft about 1 mm from the scalp using a proteinaceous glue that hardens within minutes. Nits remain attached through multiple hair washes; only mechanical removal or chemical treatment can detach them. Adult lice move rapidly along hair shafts, changing direction by rotating their bodies and using their legs to push against adjacent hairs. This combination of physical clamping and adhesive egg attachment ensures persistent infestation on the human scalp.

Location on Hair Shaft

Head lice attach to the hair shaft just above the scalp, where temperature and humidity are optimal for survival. The insect’s claws grip the cuticle of the hair, positioning the body within 1–2 mm of the skin surface. This proximity allows the louse to feed frequently without being dislodged by normal head movements.

The adult louse measures 2–3 mm in length, is flattened laterally, and exhibits a gray‑to‑brown coloration that blends with hair and skin tones. The head is broader than the thorax, and the abdomen tapers toward the rear. When viewed on a hair shaft, the body appears as a small, elongated oval that may be partially obscured by the hair strand.

Key visual indicators of lice on the shaft:

Size comparable to a sesame seed, visible only with magnification or close inspection.
Gray‑brown hue contrasting faintly with lighter hair; darker hair may conceal the insect.
• Six legs ending in sharp claws, each leg positioned near the hair’s surface.
• Movement limited to slow crawling along the shaft; rapid jumping is absent.
Nits (eggs) situated 0.5–1 mm from the scalp, cemented at an angle to the hair shaft.

These characteristics enable reliable identification of lice directly on the hair shaft without reliance on scalp examination.

Differentiating from Dandruff

Head lice are tiny, wingless insects about the size of a sesame seed, measuring 2–3 mm in length. Their bodies are flattened and grayish‑brown, with six legs ending in claw‑like hooks that enable them to cling to hair shafts. Live lice move slowly across the scalp, occasionally dropping onto clothing, and leave behind a brownish, sticky residue known as nits—oval, translucent eggs attached firmly to the base of each hair.

Dandruff consists of shed skin flakes, typically white to yellowish, ranging from fine powder to larger, visible pieces. Flakes are not attached to hair shafts and are easily brushed off with a comb or hand. The scalp may appear dry or oily, but no live organisms are present.

Key visual cues for distinguishing the two conditions:

Attachment: Lice and nits remain attached to individual hairs; dandruff flakes fall freely.
Mobility: Live lice can be seen moving when the hair is examined closely; dandruff shows no movement.
Color and texture: Lice have a solid, opaque body; nits appear translucent and oval; dandruff is irregular, powdery, and often white.
Location: Lice favor the hairline, behind ears, and neck; dandruff can occur anywhere on the scalp.
Sensation: Lice bites cause itching and occasional small red bumps; dandruff usually produces only a dry, itchy feeling without lesions.

Observing these characteristics under a magnifying lens or using a fine‑toothed comb can confirm whether a scalp problem is an infestation or merely flaky skin.

Nymphs («Baby Lice»)

Size and Color Progression

Lice that infest a human scalp range from about 0.8 mm in newly hatched nymphs to 3–4 mm in fully mature adults. Adult females are typically larger than males, reaching the upper end of the size spectrum, while nymphs increase in length with each successive molt.

Newly hatched nymph: almost transparent, pale yellow‑white.
Early‑instar nymph (first molt): light tan, still semi‑transparent.
Later nymph (second/third molt): medium brown, more opaque.
Mature adult (unfed): dark brown to reddish‑brown, body glossy.
Adult after recent blood meal: noticeably reddened abdomen, overall color deepens.

Activity Level

Lice on a human scalp are small, gray‑white insects about 2–4 mm long. Their activity level determines how often they are seen moving and how their bodies appear during different behaviors.

When lice are active, they:

Crawl rapidly across hair shafts, exposing the dorsal abdomen and legs; motion makes the body appear slightly elongated.
Pause to feed on blood at the scalp, causing the head to turn pale at the feeding site and the abdomen to swell with engorged blood.
Mate on the hair shaft; paired lice are often side‑by‑side, their bodies aligned and still.
Lay eggs (nits) attached to the hair base; during oviposition the female remains motionless, and the egg’s smooth, oval shape is visible.

During periods of low activity, lice remain motionless, clinging to hair with their claws. Their bodies become less conspicuous, appearing as tiny, flattened specks that blend with hair strands. High activity correlates with visible movement and a more pronounced, three‑dimensional silhouette, while low activity results in a static, barely detectable appearance.

Adult Lice

Size and Mobility

Head lice are small, wing‑less insects that inhabit the scalp. Adult specimens measure approximately 2–4 mm in length and 0.8–1 mm in width, comparable to a sesame seed. Nymphs emerge at 1 mm and increase in size with each molt until reaching adult dimensions. Their bodies are flattened laterally, facilitating movement through hair shafts.

Mobility relies on six legs equipped with tiny claws that grip individual strands. Lice can traverse a hair shaft at a rate of roughly 0.5 cm per second, allowing rapid repositioning across the scalp. They do not jump; locomotion is achieved exclusively by crawling. Typical movement patterns include:

Horizontal crawling along the hair shaft to locate a feeding site.
Vertical climbing to reach the scalp surface for blood meals.
Brief pauses of a few seconds between bouts of activity.

These dimensions and locomotor capabilities enable lice to remain concealed within hair while maintaining access to the host’s blood supply.

Number on the Head

Lice are tiny, wing‑less insects that cling to hair shafts and feed on blood. When examining a scalp, the visible count of live insects and nits provides the most reliable indicator of infestation severity.

Typical findings on an untreated head range from a few isolated specimens to dozens of individuals. The following categories summarize common observations:

1‑5 live lice – occasional contact, often transient, may not require immediate treatment.
6‑20 live lice – established colony, increased risk of spread; treatment generally advised.
More than 20 live lice – heavy infestation, rapid reproduction; prompt eradication necessary.

The presence of nits (eggs) attached within 1 mm of the scalp also contributes to the assessment. A count of over 10 viable nits per inch of hair commonly accompanies the higher live‑lice categories. Accurate counting should be performed with a fine‑toothed comb under adequate lighting to ensure reliable results.

Signs and Symptoms of Infestation

Itching and Discomfort

Lice on a scalp are tiny, wingless insects about the size of a sesame seed. Their bodies are flattened, gray‑white, and covered with fine hairs that cling to hair shafts. Females are slightly larger than males, but both sexes move quickly through the hair, laying eggs (nits) close to the scalp.

The primary reaction to an infestation is intense itching. The itch originates from saliva injected while the insects feed on blood; the saliva contains proteins that trigger an allergic response in the skin. This response produces:

Red, irritated patches where lice bite
Small, raised welts that may develop into pustules if scratched
A persistent, crawling sensation on the scalp

Discomfort extends beyond the itch. Repeated scratching can damage the scalp, leading to secondary bacterial infections. Swelling may cause a feeling of tightness or pressure, especially in children who are less able to control their scratching. Persistent irritation can interfere with sleep, concentration, and daily activities.

Effective management requires prompt removal of live insects and nits, combined with topical or oral treatments that eliminate the parasites and reduce inflammation. After treatment, soothing shampoos and antihistamine creams can alleviate residual itching and prevent further skin irritation.

Sores and Scratches

Lice infestations frequently produce visible irritation on the scalp. The insects themselves are small, oval, and grayish‑brown, measuring 2–3 mm in length. Their presence triggers an allergic reaction that manifests as tiny red punctures. These punctures develop into sore spots that may become crusted or ooze if scratched.

Typical characteristics of scalp sores caused by lice:

Small, well‑defined erythematous papules
Central puncture point where the insect’s mouthparts penetrate
Possible serous fluid or blood at the base after scratching
Distribution concentrated near the hairline, nape, and behind the ears

Scratches appear as linear or irregular abrasions that follow the direction of hair growth. They often have raised edges and may be covered with dried blood or crust. Repeated scratching can enlarge lesions, leading to secondary bacterial infection, characterized by increased warmth, swelling, and purulent discharge.

Distinguishing lice‑induced sores from other scalp conditions:

Presence of live or dead insects in the hair shaft
Rapid onset after exposure to an infested environment
Absence of scaling or thickened plaques typical of psoriasis or seborrheic dermatitis
Lesions confined to areas where lice are most active

Effective management includes immediate removal of lice, thorough cleansing of hair and bedding, and topical treatment of sores to reduce inflammation and prevent infection. Monitoring for signs of bacterial involvement—such as spreading erythema, pain, or pus—warrants prompt medical attention.

Visual Confirmation

Lice on a human scalp are small, wing‑less insects measuring 2–4 mm in length. Their bodies are flattened laterally, with a broad, crab‑like shape. Color ranges from pale gray to brown, often appearing translucent when unfed and darker after a blood meal. Six legs end in clawed tarsi that cling tightly to hair shafts.

Live lice move quickly, darting from one hair strand to another. They are most visible near the base of the hair, close to the scalp, where they feed. Nits—lice eggs—are oval, 0.8 mm long, and firmly cemented to the underside of hair shafts. Nits appear white or yellowish and are often mistaken for dandruff, but unlike debris they do not flake off easily.

Key visual indicators for confirming an infestation:

Adult lice: gray‑brown, about the size of a sesame seed, visible on hair close to the scalp.
Nits: oval, ivory‑colored, attached at a 45° angle to the hair shaft, resistant to removal.
Movement: rapid, erratic crawling when hair is disturbed.
Scalp irritation: localized redness or tiny puncture marks where lice feed.

Common Misconceptions

Lice and Cleanliness

Lice are tiny, wing‑less insects that inhabit the hair shafts of a human scalp. Adult head lice measure 2–4 mm in length, have a flattened body, and possess six legs ending in claw‑like tarsi that grip individual hair strands. Their coloration ranges from gray‑white to brown, often appearing translucent when the insect is unfed. Nymphs, newly hatched lice, are smaller (1–2 mm) and share the same body shape but are lighter in color. Eggs, commonly called nits, are oval, 0.8 mm long, and firmly attached to the hair shaft near the scalp by a cement‑like substance; they appear as tiny, glossy white or yellowish specks.

Cleanliness does not prevent infestation. Lice survive by feeding on blood and can proliferate on any scalp, regardless of washing frequency. However, regular grooming assists in early detection and removal. Effective control measures include:

Daily combing with a fine‑toothed lice comb to separate lice and nits.
Immediate washing of clothing, bedding, and personal items in hot water (≥ 60 °C) to kill detached insects.
Application of approved topical pediculicides according to manufacturer instructions.

Prompt identification of the characteristic size, shape, and attachment points of lice and nits is essential for managing an outbreak, independent of personal hygiene practices.

Jumping or Flying Lice

Head lice (Pediculus humanus capitis) are small, wingless insects that survive exclusively on the human scalp. Their bodies measure 2–4 mm in length, resembling tiny, flattened ovals. The head is broader than the abdomen, giving a teardrop silhouette when viewed from the side. The thorax bears six short legs equipped with clawed tarsi that grip hair shafts. Color ranges from translucent gray to brown, becoming darker after a blood meal. Eyes are absent; sensory perception relies on antennae and mechanoreceptors located on the head.

Although commonly described as “jumping” or “flying,” lice lack the anatomical structures required for aerial locomotion. They move by:

Crawling along hair shafts using their six legs.
Climbing vertically to reach the scalp, where they feed.
Transferring between hosts through direct head‑to‑head contact.

The misconception of leaping stems from the rapid, jerky motion observed when a louse is disturbed, which can give the impression of a brief hop. This movement does not involve lift-off from the hair; the insect simply releases its grip and re‑attaches a short distance away.

Key visual indicators of an infestation include:

Live insects crawling on the scalp or hair.
Nits (egg casings) firmly attached to the side of hair shafts, within 1 cm of the scalp.
Small, reddish bite marks where lice feed.

Understanding that head lice are obligate crawlers clarifies their appearance and behavior, eliminating the myth of aerial or jumping capability.

Pet Lice Transmission

Head lice are tiny, wingless insects measuring 2–3 mm in length. Their bodies are flattened, oval, and gray‑white or translucent, allowing them to blend with hair shafts. Six legs end in clawed tarsi that grasp individual strands. The abdomen contains visible segmentation, and the head is covered with fine hairs that give a slightly fuzzy appearance under magnification. Live lice move quickly, while their nits (eggs) appear as tiny, oval, yellow‑white capsules firmly attached to the base of hair shafts, often close to the scalp.

Pet lice, primarily the species Trichodectes canis (dog chewing lice) and Felicola subrostratus (cat chewing lice), cannot survive permanently on human scalps but may be transferred temporarily through direct contact with infested animals or contaminated items. Transmission occurs when adult lice or nymphs crawl onto a person’s hair or clothing during grooming, pet handling, or sharing of bedding.

Direct contact: petting or holding an infested animal for several minutes.
Indirect contact: using a comb, brush, or hat that has been in contact with the animal’s fur.
Environmental exposure: lying on surfaces where the animal has rested, especially if the area is warm and humid.

If lice from a pet reach a human head, they are usually dislodged within hours due to the unsuitable environment. However, the presence of foreign lice may cause irritation, itching, and the accidental transfer of nits that resemble human head‑lice eggs. Prompt removal of visible insects and thorough cleaning of clothing and bedding prevent secondary infestation.

Next Steps After Identification

Treatment Options

Head lice are small, wingless insects about the size of a sesame seed. Their bodies are flattened, gray‑brown, and covered with fine hairs that cling to hair shafts. Nymphs resemble adults but are lighter in color and smaller. Visible eggs (nits) appear as oval, yellow‑white shells attached firmly to the hair near the scalp.

Effective management relies on three categories: chemical agents, physical removal, and preventive measures. Selecting a method depends on infestation severity, product availability, and potential resistance.

Over‑the‑counter pediculicides containing permethrin (1 %) or pyrethrins combined with piperonyl‑butoxide. Apply according to label instructions; repeat treatment after 7–10 days to eliminate newly hatched nymphs.
Prescription‑strength preparations such as malathion (0.5 %) or ivermectin lotion (0.5 %). Use for resistant cases or when OTC products fail.
Non‑chemical options: fine‑toothed nit combs used on wet, conditioner‑treated hair; repeated combing every 2–3 days for two weeks.
Dimethicone‑based lotions that coat lice, causing dehydration without neurotoxic action. Suitable for children and pregnant individuals.
Heat therapy: hair‑drying devices that maintain scalp temperature at 50 °C for 10 minutes, effectively killing lice and nits.
Environmental control: laundering bedding and clothing in hot water (≥ 60 °C) and sealing unused items in sealed bags for two weeks.

Resistance to pyrethroid compounds is documented; therefore, confirming product efficacy through follow‑up examinations is essential. After initial treatment, inspect the scalp daily, remove residual nits with a comb, and repeat the chosen regimen if live lice persist. Consistent application of the selected protocol eliminates infestation and reduces recurrence risk.

Prevention Strategies

Head lice are small, wingless insects whose nymphs and adults appear as tiny, tan‑brown specks clinging to hair shafts. Early detection prompts immediate action, making prevention essential.

Avoid sharing combs, brushes, hats, helmets, or hair accessories.
Keep personal items separate during travel, sports, or school activities.
Wash newly acquired clothing, bedding, and towels in hot water (≥60 °C) and dry on high heat.
Apply a lice‑repellent conditioner containing dimethicone or essential oils (e.g., tea tree, neem) after each wash.
Perform regular head checks, especially after close contact with others, using a fine‑toothed comb on damp hair.
Limit prolonged close head‑to‑head contact in group settings such as camps or classrooms.

Maintain a clean environment by vacuuming upholstered furniture, carpets, and car seats weekly. Store infrequently used items in sealed plastic bags for at least two weeks to disrupt the lice life cycle. Promptly treat any confirmed case with an approved topical pediculicide, then repeat the treatment after seven days to eradicate newly hatched nymphs.

When to Seek Professional Help

Head lice are small, wingless insects about the size of a sesame seed. Adults are roughly 2–4 mm long, gray‑brown, and have a flattened body that clings tightly to hair shafts. Nymphs appear similar but are half the size. Eggs (nits) are oval, about 0.8 mm, and are firmly attached to the hair close to the scalp, often at an angle that makes removal difficult.

Seek professional assistance under the following conditions:

The infestation persists after two complete cycles of over‑the‑counter treatment applied according to label directions.
The individual experiences intense itching, redness, or swelling that suggests an allergic reaction to bites.
Secondary bacterial infection is evident, indicated by pus, crusting, or spreading erythema on the scalp.
The affected person is a child under five years old, or has a compromised immune system, making self‑treatment risky.
Multiple household members are infested and attempts at coordinated home treatment have failed.
The caregiver is unable to safely perform thorough nit removal due to limited dexterity or visual impairment.

A healthcare professional can confirm the diagnosis, prescribe prescription‑strength pediculicides, and provide guidance on environmental decontamination. Prompt referral reduces the risk of prolonged discomfort, secondary infection, and widespread transmission within families or schools.