The most reliable way to tell if you have lice is to do a wet comb test, which catches live lice about 91% of the time. Simply looking through dry hair misses most cases. Before you grab a comb, though, there are several signs that should prompt you to check in the first place.
Symptoms That Signal an Infestation
Itching is the hallmark symptom. It’s caused by an allergic reaction to louse bites, and it tends to concentrate behind the ears, at the nape of the neck, and along the crown of the head. You might also notice a tickling sensation, like something is crawling through your hair, especially at night. Scratching can lead to small sores on the scalp, which occasionally pick up bacteria and become infected.
Irritability and trouble sleeping are common too, particularly in children who can’t articulate what’s bothering them. If your child is suddenly restless at bedtime and scratching their head frequently, lice are worth investigating.
One important caveat: itching doesn’t always show up right away. Because it’s an allergic response, your body needs time to develop that sensitivity. During a first-ever infestation, weeks can pass before you feel anything. That means you can have lice and not itch at all, especially early on. This is one reason lice spread so easily in schools before anyone realizes there’s a problem.
What Lice and Nits Actually Look Like
Head lice go through three visible stages, and knowing what each one looks like helps you figure out whether an infestation is active.
- Nits (eggs): Tiny, oval-shaped specks cemented to individual hair shafts, usually within a quarter inch of the scalp. They can appear yellowish or white. Nits hatch in about 6 to 9 days.
- Nymphs: Freshly hatched lice that are smaller than adults and harder to spot. They mature through three molts over roughly 7 days before reaching full size.
- Adults: About the size of a sesame seed, tan to grayish-white, with six legs. An adult louse can live up to 30 days on a person’s head.
Nits are what most people spot first because they don’t move and they’re glued in place. Live lice are fast and avoid light, which makes them surprisingly hard to see during a casual glance.
Nits vs. Dandruff: How to Tell the Difference
This is one of the most common sources of confusion. Dandruff flakes, dry skin, hair product residue, and small keratin deposits (sometimes called “pseudo-nits”) can all look like nits at first glance. The key difference is how firmly the speck is attached to the hair.
Nits are glued to the hair shaft with a cement-like substance the female louse produces. If you try to slide a speck along the hair and it moves easily or falls off, it’s almost certainly not a nit. A real nit requires effort to pull off, and you’ll feel resistance. Nits also have a uniform, oval shape, while dandruff and keratin deposits tend to be irregular and flaky. If you’re still unsure, a magnifying glass helps. Viable nits look plump and may have a slightly dark center, while hatched nits appear translucent and empty.
Where to Look on the Scalp
Lice prefer warm, sheltered areas close to the skin. When checking yourself or someone else, focus on four zones: the crown of the head, the bangs, behind both ears, and the nape of the neck. These spots stay warm and provide easy access to the scalp for feeding. If lice or nits are present anywhere on the head, these are the areas where you’re most likely to find them.
The Wet Comb Test
A visual scan of dry hair sounds like the obvious approach, but it’s surprisingly unreliable. Research comparing the two methods found that simply looking through hair detected active infestations only about 29% of the time. Wet combing, by contrast, caught them 91% of the time. Visual inspection underestimated the true rate of active infestation by a factor of 3.5. In other words, if you just look and don’t see anything, there’s a good chance you missed it.
Wet combing works because conditioner slows lice down and makes the hair slippery enough for a fine-toothed comb to trap them. The whole process takes 5 to 15 minutes depending on hair length and thickness. Here’s how to do it:
- Step 1: Wash hair with regular shampoo, then apply a generous amount of conditioner. Don’t rinse it out yet.
- Step 2: Use a wide-toothed comb first to detangle the hair so the fine comb can pass through without snagging.
- Step 3: Switch to a lice detection comb. These have teeth spaced less than 0.3 mm apart, narrow enough to catch nymphs and adults. You can find them at any pharmacy.
- Step 4: Starting at the roots, slot the teeth of the comb against the scalp and draw it all the way down to the ends of the hair.
- Step 5: After each stroke, check the comb for lice. Wipe it on a white paper towel or rinse it in a bowl of water so you can see what’s been collected.
- Step 6: Work through the entire head section by section, then repeat the full process a second time to catch anything you missed.
White paper towels or a light-colored cloth make it much easier to spot what the comb pulls out. Live lice will be small, brown or tan, and may still be moving. Nits pulled from the hair will look like tiny dots.
What Finding Nits Alone Means
Finding nits but no live lice doesn’t automatically confirm an active infestation. Nits can remain stuck to hair long after they’ve hatched or died. The location of the nits matters: nits found more than a quarter inch from the scalp have likely already hatched or are no longer viable, since the hair has grown out. Nits found very close to the scalp are more concerning and suggest recent egg-laying activity.
If you find nits only and no live lice after a thorough wet comb, it may be a past infestation that’s already resolved. But it’s worth rechecking with the wet comb method a few days later to be sure, since nymphs are small enough to escape detection early on and could show up as they grow.
Professional Diagnosis
If you’re still uncertain after checking at home, a healthcare provider can examine your scalp using magnification or a Wood’s lamp, which emits ultraviolet light. Under this light, lice-related material on the scalp can appear as white or gray spots, making detection easier. The exam is painless and takes just a few minutes in a darkened room. Some communities also have dedicated lice clinics staffed by specialists who do high-volume screenings and can give you a definitive answer quickly.