Head lice are tiny, wingless insects that live on the human scalp and feed on blood. Adults are roughly the size of a sesame seed, about 2 to 3 millimeters long, with six legs that end in hooklike claws designed to grip hair shafts. Their color shifts depending on when they last fed: before a blood meal, they appear tan, gray, or whitish, and after feeding they darken to a reddish-brown as blood fills their translucent bodies.
What Adult Lice Look Like
A fully grown louse is flat, oval-shaped, and roughly the size of a sesame seed. It has no wings and cannot jump or fly. Instead, it crawls quickly along hair shafts using those six clawed legs, which is why spotting one can be surprisingly difficult. Lice tend to scatter from light, so you’ll rarely see them sitting still on top of the head. They prefer to stay close to the warm scalp, especially behind the ears and at the base of the neck.
Color is one of the trickier parts of identification because it changes. A louse that hasn’t fed recently looks pale, almost blending in with lighter hair or scalp skin. After feeding, its body takes on a darker, rust-colored tone from the blood visible through its semi-transparent exoskeleton. If you part the hair and see a small, elongated insect that moves fast and clings tightly to the hair, that’s a louse.
What Nymphs Look Like
When a lice egg hatches, the baby louse that emerges is called a nymph. Nymphs look like miniature versions of adult lice but are much smaller, roughly the size of a pinhead. They’re often nearly transparent or very light in color, making them even harder to see than adults. Over the course of about seven days, a nymph molts three times, growing slightly larger and darker with each stage until it reaches full adult size. During this week-long maturation, nymphs are already living on the scalp and feeding, so their presence confirms an active infestation even if you can’t find a full-sized adult.
What Nits (Eggs) Look Like
Nits are the easiest stage to find because they don’t move. They’re yellowish-white, oval-shaped, and extremely small, about the size of a knot in thread. Female lice glue each egg firmly to the side of an individual hair shaft, usually close to the scalp where body heat helps them incubate. You’ll find them most often at the back of the neck, behind the ears, and near the crown of the head.
The location of a nit on the hair shaft tells you a lot. Nits found within a quarter inch of the scalp are the ones most likely to be viable, meaning they could still hatch. Nits farther out along the hair shaft have usually either already hatched or died. After a nit hatches, the empty casing stays glued in place and gradually turns a lighter, more translucent color. These empty shells can linger in the hair for weeks or even months after an infestation is gone, which is why finding nits alone doesn’t always mean you have an active problem. The key is whether you also find live, crawling lice or nits very close to the scalp.
How to Tell Nits From Dandruff
This is one of the most common sources of confusion. Nits, dandruff flakes, and hair casts (bits of material from the hair follicle) can all look like tiny white specks in the hair. The simplest test is to try to remove them. Dandruff flakes slide off easily or can be flicked or blown away. Hair casts slip freely up and down the hair shaft when you pinch them. Nits, on the other hand, are cemented to the hair and resist removal. You’ll need to pinch the nit between your fingernails or use a fine-toothed comb to slide it off, and even then it takes deliberate effort.
Shape also helps. Nits are distinctly oval and sit at an angle on one side of the hair shaft. Dandruff tends to be irregularly shaped and sits loosely on the hair or scalp surface rather than being attached to a single strand.
How to Check for Lice
You’ll need bright light and, ideally, a fine-toothed lice comb (sometimes called a nit comb). Natural sunlight or a strong lamp works well. Part the hair in small sections and look closely at the scalp, paying particular attention to the areas behind both ears, the nape of the neck, the crown, and the bangs. These are the warmest spots on the head, and lice gravitate toward them.
Wetting the hair first can slow lice down and make them easier to spot. Comb through small sections from the scalp outward, wiping the comb on a white paper towel after each pass. Against the white background, lice and nits become much more visible. Nymphs are harder to catch because of their small size, so if you see nits close to the scalp but no crawling lice, comb again carefully. A magnifying glass can help, especially for spotting nymphs or distinguishing nits from debris.
Because lice move fast and avoid light, a single quick glance through the hair often misses them. A thorough check takes five to ten minutes of methodical combing and section-by-section examination. If you find live crawling lice or nits within a quarter inch of the scalp, that’s considered an active infestation that needs treatment.