Lice nits are the tiny eggs that head lice attach to individual strands of hair, close to the scalp. They’re oval-shaped, roughly 0.8 mm long, and range in color from yellowish-brown (when viable) to white (after hatching). If you or your child has been diagnosed with head lice, the nits are usually the most visible sign of an infestation, and they’re also the hardest part to get rid of because of the remarkably strong glue that bonds them to hair.
What Nits Look Like Up Close
Nits are teardrop-shaped specks found within about a quarter inch of the scalp. A viable nit, one that still contains a developing louse, tends to be yellowish-brown. Once the egg has hatched or died, the empty shell (called a casing) turns white or translucent and may be found farther from the scalp as the hair grows out.
People often confuse nits with dandruff, dried hair product, or other debris. The simplest test: try to flick it off. Dandruff and product residue slide easily along the hair strand or fall away when you touch them. A nit won’t budge. It’s cemented in place and can only be removed by pinching it between your fingernails and sliding it firmly down the entire length of the hair, or by using a fine-toothed nit comb.
How Nits Stay Attached
A female louse produces up to about 10 eggs per day, and she glues each one individually to a hair shaft using a secretion from a specialized gland. Scientists once assumed this glue was made of chitin, the same material in insect shells, but it’s actually protein-based. The proteins solidify into a thin, water-resistant film almost immediately after being deposited, forming a tight sheath around both the egg and the hair.
Research published in Nature characterized two key proteins in this sheath. Their molecular structure includes repeating sequences that fold into layered, sheet-like formations, which is what gives the glue its exceptional grip. It resists water, shampoo, and most solvents. This is why simply washing your hair won’t remove nits, and why mechanical removal with a comb or fingernails remains essential even after chemical treatments kill the live lice.
How Long Nits Take to Hatch
Nits hatch in 6 to 9 days, with about a week being typical. The tiny louse that emerges, called a nymph, is roughly the size of a pinhead and takes another seven days to mature into a full adult capable of laying its own eggs. That means the window from a single egg being laid to a new generation of egg-laying adults is roughly two weeks.
This timeline matters for treatment. Most lice treatments kill live lice but don’t reliably destroy all nits. A second treatment roughly 7 to 10 days after the first catches any nymphs that hatched from surviving eggs before they’re old enough to reproduce. Skipping that second round is one of the most common reasons infestations come back.
Where to Look on the Head
Lice prefer warm, sheltered areas of the scalp. The most common spots for nit deposits are behind the ears and along the nape of the neck, though they can appear anywhere. When checking for nits, part the hair in small sections under bright light and look near the base of the hair shaft, within a quarter inch of the scalp. Nits found much farther out have likely already hatched or are no longer viable, since they were laid close to the scalp and have moved away as the hair grew.
Can Nits Survive Away From the Head?
Nits need the warmth of the human scalp to develop. If a nit somehow ends up on a pillowcase, hat, or brush, it will generally die within a week and cannot hatch at temperatures lower than those found close to the scalp. This is why head-to-head contact is the primary way lice spread. Worrying about furniture, carpets, or classroom cubbies is largely unnecessary, though washing pillowcases and hats in hot water after treatment is a reasonable precaution.
Removing Nits Effectively
Because the protein glue is so durable, the most reliable removal method is a specialized nit comb with very tightly spaced teeth. A study comparing commercial lice combs found that metal combs significantly outperformed plastic ones. The most effective metal comb in the study had teeth spaced just 0.09 mm apart, compared to 0.23 mm for the best plastic option. That tighter spacing catches both nits and the smallest nymphs that wider-toothed combs miss.
For best results, work through wet, conditioned hair in small sections. The conditioner helps the comb glide and makes it easier to see the nits. Wipe the comb on a white paper towel after each pass so you can spot what’s being removed. Plan on spending 30 to 60 minutes for a thorough combing session, and repeat every few days for at least two weeks to catch any nits you missed.
Why “No-Nit” School Policies Are Fading
Many schools historically required children to be completely nit-free before returning to class. Both the American Academy of Pediatrics and the National Association of School Nurses now recommend against these policies for several reasons. Nits found more than a quarter inch from the scalp are unlikely to hatch. They’re cemented to hair and essentially impossible to transfer to another person. Misdiagnosis during school nit checks by non-medical staff is common, with dandruff and other debris frequently mistaken for nits. And the lost school days create a burden on students and families that far outweighs any realistic transmission risk.
The CDC’s current guidance reflects this shift: children with head lice do not need to be sent home early. They can finish the school day, get treated that evening, and return to class the next day after starting appropriate treatment.