To confirm lice are completely gone, you need to find zero live lice and zero new nits (eggs) close to the scalp over a full 2 to 3 week monitoring period after your last treatment. A single check isn’t enough because eggs can survive treatment and hatch days later. The only reliable way to know for sure is consistent, repeated combing checks using the right technique and knowing exactly what to look for.
Why One Check Isn’t Enough
Lice eggs take 8 to 9 days to hatch, and the newly hatched nymphs need another 7 to 12 days to mature into adults that can lay new eggs. That means a missed egg could restart the entire cycle up to three weeks after you thought treatment was finished. Most lice treatments kill live lice but don’t reliably kill all eggs, which is why the CDC recommends checking hair and removing nits every 2 to 3 days for 2 to 3 weeks after treatment.
If you stop checking too early and even one viable egg survives, you can end up right back where you started within a few weeks.
Use Wet Combing, Not Visual Checks
Looking through dry hair and scanning for lice with your eyes is surprisingly unreliable. A study published in JAMA Dermatology found that visual inspection caught active infestations only about 29% of the time, while wet combing with a fine-toothed nit comb detected them over 90% of the time. That’s a massive difference, and it means you could visually inspect someone’s head, see nothing, and still miss an active case.
To wet comb effectively, saturate the hair with conditioner or a detangling spray. This slows live lice down and makes them easier to catch. Use a fine-toothed metal nit comb (plastic combs from drugstore kits are less effective) and work through the hair in small sections from the scalp to the tips. Wipe the comb on a white paper towel after each pass so you can clearly see anything you’ve pulled out. Pay extra attention behind the ears and along the nape of the neck, where lice prefer to lay eggs.
How to Tell Live Nits From Dead Ones
Finding nits after treatment doesn’t automatically mean you still have an active infestation. The key is distinguishing viable eggs from empty shells. Here’s what to look for:
- Live nits are tan, golden brown, or amber. They look plump and shiny, and they sit within a quarter inch of the scalp. Under magnification, you can sometimes see a small dark spot inside, which is the developing embryo.
- Dead or hatched nits are white, translucent, or grayish. They look dull, flattened, or hollow, and they’re typically more than a quarter inch from the scalp. Since hair grows about half an inch per month, a nit sitting half an inch or more from the scalp was laid at least a month ago.
If the only nits you’re finding are white, dull, and far from the scalp, those are old casings. They’re cosmetically annoying but not a sign of active lice. The ones that matter are the shiny, brown ones glued close to the scalp. Those need to be removed immediately.
The 2 to 3 Week Monitoring Schedule
After your final treatment, set up a combing schedule: wet comb every 2 to 3 days for a full 2 to 3 weeks. Each session, you’re looking for two things. First, any live crawling lice, which would mean treatment didn’t fully work. Second, any new nits within a quarter inch of the scalp, which would mean a surviving female is still laying eggs.
Here’s how to interpret what you find at each check:
- No live lice, no new close-to-scalp nits: Good. Keep checking on schedule until you’ve hit the 2 to 3 week mark with consistent clear results.
- A few lice moving slowly 8 to 12 hours after treatment: This is normal. The treatment is still working. Comb them out and continue monitoring.
- Lice still moving normally 8 to 12 hours after treatment: The product likely didn’t work. This is especially common now because resistance to over-the-counter lice treatments has increased dramatically. A meta-analysis of 20 studies found that 59% of head lice populations worldwide are resistant to the most common drugstore treatments, and after 2015 that rate reached 82%. If your product didn’t work, you’ll need a different approach.
- New nits appearing close to the scalp days after treatment: An active infestation is still going. Re-treat and restart your monitoring window.
You can consider yourself lice-free when you’ve completed the full monitoring period with zero live lice found and zero new viable nits at any check.
What to Do If Treatment Isn’t Working
Resistance to permethrin, the active ingredient in most over-the-counter lice shampoos, is now widespread. If you’ve followed instructions carefully and lice are still active 8 to 12 hours later, the product itself is the problem, not your technique. Prescription options work through different mechanisms that resistant lice can’t evade. Your doctor or pharmacist can recommend an alternative.
Manual removal with a nit comb is always effective regardless of resistance, though it requires patience. Some families use wet combing every 2 to 3 days as their primary treatment method, skipping chemical products entirely. This works because you’re physically removing lice faster than they can reproduce, but you have to be thorough and consistent for the full cycle.
Cleaning Your Home Without Overdoing It
Lice are human parasites. They need blood meals to survive and can only last up to three days off a human head. Eggs can survive away from the host for a similar period, but they won’t hatch at temperatures lower than what the scalp provides. This means your home doesn’t need deep sanitizing, just a few targeted steps.
Wash pillowcases, sheets, and any recently worn hats or scarves in hot water above 60°C (140°F) for at least 10 minutes, then run them through a hot dryer cycle. For items you can’t wash, seal them in a plastic bag for 10 days. At room temperature or cooler, all lice and eggs will be dead well within that window. Vacuum upholstered furniture and car seats, then move on. Spraying furniture with pesticide products is unnecessary and doesn’t meaningfully reduce reinfestation risk.
Focus the bulk of your effort on the head, not the house. The scalp is where the infestation lives and where it will either survive or end.
Checking Household Members
If one person in your home had lice, wet comb everyone else every 2 to 3 days while monitoring the treated person. Lice spread through direct head-to-head contact, so household members, especially children who share beds or play closely together, are the most likely source of reinfestation. Treating one person while ignoring a silent case in a sibling is one of the most common reasons lice seem to “come back” after successful treatment. The lice never actually left the household.