Head lice are tiny, wingless insects that live on the human scalp and feed on blood. Adult lice are about the size of a sesame seed, grayish or pale in color, and have six legs. But what you’re most likely to spot first aren’t the lice themselves. It’s their eggs, called nits, glued to individual hair strands close to the scalp.
What Adult Lice Look Like
A fully grown head louse is roughly 2 to 3 millimeters long, comparable to a sesame seed or a strawberry seed. They’re gray or yellowish and somewhat flat, with six clawed legs designed to grip hair shafts. After feeding, their bodies can take on a darker, reddish-brown tint from the blood inside them. They move fast and avoid light, which is why you’ll rarely catch one sitting still during a visual check. Lice don’t fly or jump. They crawl, and they’re surprisingly quick at it.
You’re most likely to find adult lice at the back of the head, along the neckline, and near the ears. These are the warmest areas of the scalp, and lice prefer them for laying eggs and feeding.
What Nymphs Look Like
After a nit hatches, the baby louse (called a nymph) is about the size of a pinhead. Nymphs look like smaller versions of adult lice but are nearly translucent, making them extremely hard to see with the naked eye. They go through three growth stages over about seven days before reaching full adult size. During this period, they stay close to the scalp because they need warmth and frequent blood meals to survive.
What Nits Look Like on the Hair
Nits are oval-shaped and tiny, smaller than a pinhead. They range from white to yellowish-brown in color. A viable nit (one that hasn’t hatched yet) tends to be darker and sits within about a quarter inch of the scalp, where body heat keeps it warm enough to develop. Nits that are farther than a quarter inch from the scalp have most likely already hatched or are dead. This distance rule is a useful way to gauge whether an infestation is still active or whether you’re looking at old remnants.
Each nit is cemented to an individual hair strand at an angle. The glue-like substance female lice use is remarkably strong, and this is actually the most reliable way to tell nits apart from other things in the hair. Unlike dandruff or dry skin flakes, nits don’t brush or flick off easily. If you try to slide a speck along the hair shaft and it won’t budge, it’s likely a nit. Dandruff falls away with minimal effort.
Nits vs. Dandruff and Other Look-Alikes
This is one of the most common sources of confusion. Dandruff flakes are white, irregularly shaped, and scattered loosely through the hair and on the scalp. They come off easily when you comb or shake the hair. Nits, by contrast, are uniform in shape, attached firmly to one side of a hair strand, and clustered in specific zones (behind the ears, along the neckline). They won’t flick off when you run your fingers through the hair.
Other things that can mimic nits include hair casts (thin, white tubes that slide freely along the hair shaft), residue from hair products, and sand or dirt particles. The key test is always the same: can you easily remove it? If yes, it’s not a nit.
What Lice Bites Look Like on Skin
Lice feed by biting the scalp, and many people develop small, itchy bumps at the bite sites. On lighter skin, these bumps typically appear red. On darker skin tones, they can be harder to see and may look slightly darker than the surrounding skin or be felt as raised spots rather than seen. The most common locations for visible bite marks and irritation are the scalp, the back of the neck, and the shoulders.
Persistent scratching can break the skin and lead to small sores, which sometimes get infected. If you notice crusty patches or oozing spots along the hairline or behind the ears, that’s usually a sign of a longer-standing infestation where scratching has caused secondary skin damage.
How to Actually Find Them
Simply looking through dry hair and scanning for lice is not very effective. A study comparing the two main detection methods found that visual inspection alone missed active infestations about 70% of the time, underestimating the true number of cases by a factor of 3.5. Wet combing, on the other hand, correctly identified active infestations in over 90% of cases.
To wet comb, saturate the hair with water and a generous amount of conditioner. The conditioner slows lice down and makes it easier for a fine-toothed lice comb to catch them. Starting at the scalp, pull the comb slowly through small sections of hair from root to tip. After each pass, wipe the comb on a white paper towel or cloth. Against the white background, lice and nits become much easier to spot.
Focus your combing on the areas behind the ears and along the base of the skull. Work in good lighting, and take your time. A thorough wet combing session on shoulder-length hair can take 15 to 20 minutes. If you find live lice or nits within a quarter inch of the scalp, the infestation is active and needs treatment. If you only find nits well away from the scalp and no live lice, the infestation has likely already run its course or been treated.
What You’re Looking For at a Glance
- Adult lice: sesame-seed-sized, gray or yellowish, six legs, fast-moving, found close to the scalp
- Nymphs: pinhead-sized, nearly translucent, same shape as adults but much smaller
- Viable nits: oval, yellowish-brown or white, glued to the hair within 1/4 inch of the scalp, won’t flick off
- Old or hatched nits: white or clear, found farther than 1/4 inch from the scalp, still firmly attached
- Bite reactions: small raised bumps on the scalp, neck, and behind ears, with possible sores from scratching
A magnifying glass and good lighting make identification much easier, especially for nymphs and nits. If you’re unsure whether what you’re seeing is a nit or a flake, the removal test is your simplest tool: pinch it and try to slide it off the hair. If it stays put, treat it as a nit.