Head lice are tiny, flat insects about the size of a sesame seed, with six legs that end in hooklike claws designed to grip hair. Adults are tan, gray, or white, and they stay close to the scalp where they feed on blood. But lice look different at each stage of their life cycle, and knowing what to look for at every stage is the key to catching an infestation early.
What Adult Lice Look Like
An adult head louse is 3 to 4 millimeters long, roughly the size of a sesame seed. Females are slightly larger than males. Their bodies are flat, elongated, and wingless, with a color that ranges from tan to grayish-white. After feeding, they can appear darker or reddish-brown because of the blood visible through their translucent bodies.
Each of their six legs ends in a curved claw perfectly shaped for gripping individual hair strands. These claws are why lice don’t just fall off when you shake your head or run your fingers through your hair. Under magnification, their bodies look segmented, with a distinct head, thorax, and abdomen. To the naked eye, though, they mostly look like tiny, pale, slow-moving specks that scurry away from light when you part the hair.
What Nits (Eggs) Look Like
Nits are the eggs that female lice cement directly onto individual hair shafts, usually within a quarter inch of the scalp where the warmth helps them incubate. They’re teardrop-shaped, smaller than adult lice, and attached at an angle to the hair. A single nit is easy to mistake for a flake of dandruff or a bit of debris, which is why understanding their specific features matters.
Living nits can be white, yellow, beige, or pale brown depending on how far along they are in development. They take about a week to hatch. Once a nit has hatched, the empty casing left behind turns white, gray, or translucent and stays glued to the hair as it grows out. Dead nits that never hatched tend to look brown or black. If you spot something on a hair strand and aren’t sure what it is, try sliding it with your fingers. Nits are firmly attached and resist being moved, while dandruff and other debris flake off easily.
What Nymphs Look Like
When a nit hatches, what emerges is a nymph: a baby louse that looks like a smaller version of the adult. Nymphs are harder to spot because of their size. They go through several molts over about 9 to 12 days before reaching full adult size. During this stage they’re often pale and nearly transparent, making them easy to miss against a light scalp. As they mature and feed, they gradually darken toward the tan or gray color of an adult.
Nits vs. Dandruff and Other Lookalikes
The most common mix-up is between nits and dandruff. Dandruff flakes are irregularly shaped, white, and fall off the hair easily when you touch them. Nits are oval, firmly cemented to the shaft, and won’t budge without deliberate pulling or a fine-toothed comb.
Another lookalike is hair casts, sometimes called pseudonits. These are small, white, shiny tubes that wrap around the hair shaft and can look convincingly like nits at first glance. The difference is that hair casts slide freely along the strand when you pinch them, while a true nit stays locked in place. Hair casts also tend to be longer (2 to 7 millimeters) and encircle the hair completely rather than sitting on one side like a nit does. Hairspray residue and product buildup can also mimic nits, but again, they lack that stubborn attachment.
Where to Look on the Head
Lice prefer warm spots. The areas behind the ears and along the nape of the neck are the most common places to find both live lice and nits. When checking someone’s head, work in bright natural light or use a strong lamp. Part the hair in small sections and look at the first quarter inch of hair closest to the scalp. A fine-toothed lice comb dragged through wet, conditioned hair is more reliable than a visual search alone, because live lice move quickly and avoid light.
Nits farther than half an inch from the scalp have usually already hatched or are no longer viable, since the scalp’s warmth is needed for incubation. Finding only distant, empty casings without any nits close to the scalp or any live lice may mean the infestation has already resolved.
How Other Types of Lice Differ
Humans can host three species of lice, and they look noticeably different from one another. Head lice have the elongated, narrow body described above. Body lice look nearly identical to head lice in shape and size but live in clothing seams rather than on hair, only moving to the skin to feed. You’re far more likely to find body lice in unwashed clothing than on the body itself.
Pubic lice, often called crabs, are visually distinct. They’re broader, flatter, and rounder than head lice, measuring only 1.1 to 1.8 millimeters, about the size of a pencil tip. Their wider body and prominent front claws give them a crab-like appearance that’s easy to distinguish from head or body lice if you can see them clearly. They’re typically found in coarse body hair, including the pubic area, and occasionally in eyebrows or eyelashes.