Lice are small, wingless insects about the size of a sesame seed, with six legs, a flat oval body, and no wings. An adult head louse measures roughly 3 to 4 millimeters long and can range in color from white to tan, gray, or reddish-brown depending on when it last fed. They’re visible to the naked eye but easy to miss, especially in thick or dark hair.
What Adult Head Lice Look Like
An adult head louse has an elongated, somewhat flattened body that’s longer than it is wide. Female lice are about 3 to 4 mm long, while males run slightly smaller. Each of the six legs ends in a hook-like claw designed to grip individual hair strands, which is why lice are so difficult to shake loose once they’ve latched on.
Color is one of the trickiest parts of identification. A louse that recently fed on blood will look reddish-brown, while one that hasn’t eaten recently may appear tan, gray, or nearly white. This color-shifting ability also helps lice blend in with the scalp and hair around them. In lighter, thinner hair, they’re easier to spot. In dark or coarse hair, you may need a fine-toothed comb and good lighting to find them.
Lice move exclusively by crawling. They cannot jump, fly, or swim. Their top speed is less than four inches per minute, so they tend to stay close to the scalp where they feed and where the warmth keeps their eggs viable.
What Nits Look Like on the Hair
Nits are lice eggs, and they’re the most common sign people notice first. They’re tiny ovals, smaller than a pinhead, and they appear white or yellowish-brown. A female louse cements each egg directly onto a hair shaft, usually within a quarter inch of the scalp. That cement is strong enough that nits don’t slide or flick off the way dandruff does.
This is the simplest way to tell nits from dandruff: try to pull the white speck off the hair strand. Dandruff flakes away easily. A nit stays put. You’ll typically need to pinch the hair between your fingernails and slide the nit down the shaft to remove it. Nits take 7 to 12 days to hatch, so finding nits close to the scalp usually means an active infestation, while nits further down the hair shaft are older and may already be empty shells.
Nymphs: The In-Between Stage
When a nit hatches, what emerges is a nymph, which is essentially a miniature version of the adult. Nymphs are smaller and harder to see, but they have the same body shape and six legs. They go through three growth stages over about 9 to 12 days before reaching full adult size. During this period, they’re translucent or very light in color, making them especially difficult to spot against a pale scalp. By the time they mature, they darken and become easier to identify.
Head Lice vs. Body Lice
Head lice and body lice look nearly identical to a casual observer. Body lice are about 10 to 20 percent larger, with slightly thinner antennae and less pronounced indentations along the abdomen. The real difference is where you find them. Head lice live on the scalp and attach their eggs to hair. Body lice live in clothing seams and only move to the skin to feed. If you’re finding lice on your head and in your hair, you’re dealing with head lice.
What Pubic Lice (Crabs) Look Like
Pubic lice look distinctly different from head or body lice. They’re much smaller, only about 1.1 to 1.8 mm long (roughly the size of a pencil tip), and their bodies are broader and flatter, giving them a crab-like shape that earned them the nickname “crabs.” Their oversized front claws are built to grip the thicker, more widely spaced hair found in the pubic region, armpits, and sometimes eyebrows. If you see a louse that looks round and squat rather than elongated, it’s likely a pubic louse.
How to Spot Lice During a Check
The best way to find lice is to work in bright light, ideally natural daylight or a strong lamp. Wet the hair and use a fine-toothed nit comb, starting at the scalp and pulling outward to the ends. After each pass, wipe the comb on a white paper towel or cloth. Against a white background, even small nymphs and nits become visible.
Focus on the areas behind the ears and along the nape of the neck. These are the warmest spots on the scalp, and lice prefer them for laying eggs. Part the hair in small sections and look at the base of the hair shafts for nits. If you see small oval shapes that resist being pulled off, that’s a strong sign of lice.
Live lice tend to scurry away from light and disturbance, so combing is more reliable than simply looking. A dry visual check can miss an infestation entirely, particularly when only a few adult lice are present. Most people with head lice have fewer than 10 live lice on their scalp at any given time, which is why the eggs are often easier to find than the insects themselves.