Up close, a head louse is a flat, wingless insect about 2 to 3 millimeters long, roughly the size of a sesame seed. It has six legs, each tipped with a curved claw designed to grip hair shafts, and its color ranges from tan to grayish-white, though lice that have recently fed can appear darker brown or almost black. Knowing what each life stage looks like helps you figure out whether what you’re seeing in hair is actually lice or something else entirely.
Adult Lice Up Close
An adult head louse has an elongated, oval body that is distinctly longer than it is wide. The outer shell is somewhat translucent, which is why the insect’s color shifts depending on whether it has fed recently. A louse that just took a blood meal from the scalp looks darker, while one that hasn’t fed in a while appears more of a dirty white or light gray. The body has no wings, and it cannot jump or fly. It moves exclusively by crawling.
The six legs are clustered near the front of the body, each ending in a hook-like claw that works like a pincer. These claws are perfectly sized to wrap around a human hair strand, which is why lice are so difficult to shake loose with regular brushing. Under magnification, you can see the claws snap shut around the hair shaft the way a hand grips a rope. The louse also has short antennae and a small head relative to its body, with mouthparts designed to pierce the scalp and feed on blood.
What Nits Look Like on Hair
Nits are lice eggs, and they’re considerably smaller than adult lice. Each one measures about 0.8 mm long by 0.3 mm wide, making them visible to the naked eye but easy to overlook. They have a teardrop shape and are cemented to individual hair strands with a glue-like substance the female louse produces. This bond is strong enough that nits won’t slide off when you run your fingers along the hair or brush through it.
Live nits are usually white to yellowish-brown and sit close to the scalp, typically within a quarter inch of the skin surface. That proximity matters because nits need warmth from the scalp to develop. Once a nit hatches or dies, the empty casing stays glued to the hair and gradually shifts farther from the scalp as the hair grows out. These empty casings look more translucent or grayish compared to viable eggs. If you find nits more than about a quarter inch from the scalp, they’re most likely already hatched or no longer alive.
Nymphs: The In-Between Stage
After a nit hatches, the immature louse that emerges is called a nymph. Nymphs look like miniature versions of adult lice, with the same body shape and six clawed legs, but they’re roughly the size of a pinhead. They’re pale and nearly transparent at first, making them harder to spot than adults. A nymph takes about seven days to mature into a full-sized adult, growing slightly larger and darker with each molt.
How Lice Differ From Dandruff
This is the comparison most people are really trying to make when they search for what lice look like. Both nits and dandruff can appear as small white or yellowish specks in the hair, but they behave very differently.
The simplest test: try to flick or pull the speck off the hair strand. Dandruff flakes slide off easily because they’re just loose skin from the scalp. Nits won’t budge without deliberate effort because they’re glued in place. Dandruff also tends to appear as irregular, flat flakes that can look greasy or dry, and it falls from the scalp onto the hair and shoulders. Nits, by contrast, have that distinctive teardrop shape and attach to the side of individual hair shafts rather than sitting loosely on top.
Location is another clue. Dandruff affects the scalp itself and sheds outward. Nits are found on the hair, not the scalp, and cluster in warm areas behind the ears and along the nape of the neck. The lice themselves are tan to dark brown and have visible legs, so if you spot something that’s clearly an insect crawling through the hair, that’s not dandruff.
Pubic Lice Look Different
If you’re checking areas other than the head, it helps to know that pubic lice (sometimes called crabs) are a separate species with a noticeably different shape. Where head lice have an elongated body, pubic lice are short, broad, and flat, giving them a distinctly crab-like appearance. They’re also smaller, measuring about 1.1 to 1.8 mm, closer to the size of a pencil tip. Their second and third pairs of legs are thicker and sturdier than those of head lice, built to grip the coarser hair found in the pubic region.
How to Spot Them in Practice
Adult lice avoid light and move quickly through hair, so they’re often harder to catch sight of than nits. The most reliable method is to wet the hair, apply conditioner to slow the lice down, and comb through small sections with a fine-toothed lice comb. Wipe the comb on a white paper towel after each pass. Against the white background, adult lice show up as small dark specks with visible legs, and nits appear as tiny oval dots stuck to individual hairs.
Focus your search on the areas closest to the scalp where warmth is greatest: behind the ears, along the hairline at the back of the neck, and at the crown. Nits in these zones that are within a quarter inch of the scalp are the ones that signal an active situation. Scattered empty casings farther out on the hair shaft, with no live lice or close-to-scalp nits, generally indicate an old infestation that has already resolved.