The most reliable sign of head lice is finding a live louse or nit (egg) attached to a hair shaft. Itching is the symptom most people associate with lice, but it can take four to six weeks to develop after the first infestation, meaning you could have lice for over a month before feeling any itch at all. Knowing what to look for and how to check properly makes the difference between catching an infestation early and missing it entirely.
Why Itching Isn’t Always the First Clue
The itching from head lice comes from an allergic reaction to their saliva, not from the bugs crawling around. Your immune system needs time to develop that sensitivity. During a first-ever infestation, four to six weeks can pass before the itching kicks in. If you’ve had lice before, the reaction tends to start sooner because your body already recognizes the allergen.
When itching does show up, it’s most intense behind the ears and along the back of the neck, where lice prefer to feed and lay eggs. You might also notice a tickling sensation on the scalp, as if something is moving through your hair. Some people develop small red bumps from scratching, which can sometimes be mistaken for a rash or eczema.
What Lice and Nits Look Like
Adult lice are dark in color and roughly the size of a poppy seed. They have six legs and move quickly, which is why spotting one by simply parting the hair can be difficult. They avoid light and scurry away when you disturb the hair.
Nits are easier to find because they don’t move. They’re tiny oval-shaped eggs, white or yellowish-brown, glued firmly to individual hair strands close to the scalp. Adult lice lay eggs within a few millimeters of the scalp surface because the warmth is needed for incubation. Nits hatch in about six to nine days, and the newly hatched nymphs mature into adults roughly seven days after that. So from a single egg, a fully grown louse can develop in about two weeks.
Where you find nits on the hair shaft tells you whether an infestation is active. Nits found within about 6 millimeters (roughly a quarter inch) of the scalp strongly suggest a current, active infestation. Nits found only farther out on the hair shaft are more likely remnants of a previous infestation that has already been treated or resolved, since hair growth gradually carries old, empty egg casings away from the scalp over time.
How to Tell Nits From Dandruff
This is one of the most common sources of confusion. Both nits and dandruff flakes are small, whitish, and show up near the scalp. The fastest way to tell them apart is to try moving them. Dandruff is a flake of dry skin that slides off easily when you run your fingers through your hair or shake your head. Nits are cemented to the hair shaft with a glue-like substance the louse secretes when laying the egg. If you pinch a suspected nit between your fingers and try to slide it along the strand, it will resist. You’ll need to pull firmly or use a fine-toothed comb to remove it.
Location offers another clue. Nits are almost always found very close to the scalp, within a few millimeters. Dandruff can appear anywhere on the head or scattered throughout the hair. The farther away from the scalp you find a white speck, the more likely it’s dandruff rather than a viable egg.
The Best Way to Check for Lice
A visual scan of dry hair catches lice only about 30 to 40 percent of the time because adult lice move fast and hide well. Wet combing is far more effective. Here’s how to do it:
- Wet the hair thoroughly. Apply a generous amount of regular hair conditioner, or a thick product like petroleum jelly or a dimethicone-based detangler. This slows lice down significantly, making them easier to catch on the comb.
- Use a fine-toothed nit comb. These have teeth spaced closely enough to trap both adult lice and nits. Standard combs and brushes won’t work.
- Comb from the scalp outward. Place the comb flat against the scalp and draw it all the way to the end of the hair in one steady stroke. After each pass, wipe the comb on a white paper towel or tissue and look for lice or nits.
- Work in sections. Divide the hair into small sections using clips. Comb each section at least twice, paying extra attention to the areas behind the ears and at the nape of the neck.
Good lighting matters. Natural daylight or a bright lamp aimed at the scalp will help you spot the tiny, dark-colored adult lice on the paper towel. Nits on the comb will look like small, firm specks that don’t flick away easily.
Signs That Suggest Lice but Aren’t Definitive
Several symptoms can point toward lice without confirming them on their own. Persistent scalp itching, especially behind the ears and at the nape, is the most common. A feeling of something moving in the hair is another frequently reported sensation. Small red bumps or sores on the scalp, neck, or shoulders can develop from repeated scratching, and in some cases these can become infected with bacteria if the skin breaks.
Difficulty sleeping is sometimes an overlooked sign. Lice are most active in the dark, and some people notice increased scalp irritation at night before they ever spot a bug during the day.
None of these symptoms are unique to lice. Dry scalp, eczema, allergic reactions to hair products, and other conditions can cause similar itching. The only way to confirm an infestation is to find a live louse or a viable nit attached close to the scalp. If you’ve done a thorough wet combing and found nothing, the itching is likely caused by something else.
Checking Others in Your Household
Lice spread through direct head-to-head contact, which is why they move easily between children who play closely together and between kids and parents during hugs, bedtime, or shared activities. If one person in your household has confirmed lice, check everyone else using the wet combing method. Lice don’t jump or fly, so casual proximity in a room isn’t enough for transmission, but sharing hats, brushes, or pillows can occasionally spread them.
Focus your checks on anyone who has had close physical contact with the person who has lice. You don’t need to treat someone who shows no evidence of lice or nits, even if they share a home with someone who does. Treating preventively without finding lice isn’t recommended and can contribute to treatment resistance over time.