Nits are the eggs laid by head lice, glued directly onto individual strands of hair close to the scalp. They’re tiny, oval, and yellowish-white, roughly the size of a knot in a thread. If you’ve found something small and stubborn clinging to hair that won’t flake off when you brush at it, you’re likely looking at a nit.
What Nits Look Like
Nits are oval-shaped and typically yellowish-white, though their color can vary slightly depending on whether they contain a developing louse or have already hatched. They sit on the hair shaft itself, not on the scalp, and they’re small enough to be mistaken for dandruff or a tiny bit of debris. The key difference: dandruff flakes off easily when you touch it. Nits don’t. They are cemented in place and will not slide or brush away without effort.
If you also spot small brown or black dots on the scalp or see tiny bugs crawling, that confirms a lice infestation rather than a simple case of dry scalp.
How Nits Attach to Hair
Female lice produce a protein-based glue that bonds each egg to the hair shaft. This cement is chemically similar to human hair itself, which is part of why it’s so difficult to remove. The sheath hardens around the base of the nit, locking it in place with a structure tough enough to survive washing, brushing, and most shampoos.
Lice lay their eggs close to the scalp because the warmth is essential for development. A viable nit is typically found less than 6 millimeters from the skin surface. Nits found farther down the hair shaft have usually either already hatched or died, since they can’t develop without consistent body heat. That said, it’s difficult to tell viable nits from empty ones without a microscope, so distance from the scalp is only a rough guide.
How Long Nits Take to Hatch
A nit hatches in about 6 to 9 days after being laid. The baby louse that emerges, called a nymph, begins feeding on blood from the scalp almost immediately. Once hatched, the empty eggshell stays glued to the hair and gradually moves farther from the scalp as the hair grows out. These empty casings are often lighter in color and can linger in the hair for weeks or months, making it look like an infestation is still active when it may not be.
Nits that get separated from a human host, whether on a pillowcase, hairbrush, or hat, lose access to the warmth they need. They usually die within a week. Adult lice are even more fragile off the head, surviving no more than 12 to 24 hours without a blood meal.
Do Nits Mean an Active Infestation?
Not necessarily. Finding nits close to the scalp suggests a possible active infestation, but research from the Canadian Paediatric Society shows this is only a modest predictor. In one study of children who had five or more nits within 6 millimeters of the scalp, fewer than 32% actually had an active infestation with live lice. Among children with fewer than five nits near the scalp, only 7% went on to develop an active case.
The most reliable sign of a current infestation is finding a live, crawling louse. Nits alone, especially those sitting more than a centimeter from the scalp, often represent an old or resolved case.
Why Nits Are Hard to Treat
Most over-the-counter lice treatments kill live lice effectively but do little to the eggs. Common drugstore products based on permethrin or pyrethrins are not reliably ovicidal, meaning they leave nits intact. This is why a second treatment 7 to 10 days later is standard: it catches newly hatched nymphs before they can mature and lay more eggs.
Some prescription treatments have stronger egg-killing properties. Malathion-based products, for example, are more effective against unhatched nits than permethrin and lead to lower re-infestation rates. Hot air has also been shown to kill more than 88% of nits in studies, though it’s less consistent against live lice. Regardless of the product used, no single treatment is 100% effective, and repeat applications or manual removal are almost always part of the process.
How to Remove Nits
Because treatments alone won’t clear every egg, manual removal with a fine-toothed nit comb is the most reliable way to get rid of them. The most effective approach is wet combing: apply a thick layer of hair conditioner, which immobilizes any live lice and makes the hair slippery enough for the comb to glide through. Start with a wide-toothed comb to detangle, then switch to progressively finer combs. Detection combs designed for lice should have tooth spacing of less than 0.3 millimeters, narrow enough to catch both nits and nymphs.
Work through the hair in small sections, wiping the comb on a white paper towel after each pass so you can see what you’re pulling out. The whole process takes about 5 to 15 minutes depending on hair length and thickness, and it needs to be thorough. The phrase “nit-picking” exists for a reason: missing even a few viable eggs can restart the cycle. Repeat the combing every few days for at least two weeks to catch any nits that were missed or any new nymphs before they reach adulthood.
Some parents use vinegar or specialized enzyme sprays marketed to dissolve the nit cement. While these can loosen the bond slightly, none eliminate the need for careful combing. The protein glue is simply too durable for any rinse to fully break down on its own.