You did everything the box told you to do. A few days later you checked the part lines again, and there they were — tiny, moving, right back on your child’s scalp. It feels like the treatment failed, or like these are some unkillable super lice. Usually it’s neither. Lice that return almost always trace to a source you can find and fix: a head at home that never got treated, live eggs the first pass left behind, a second treatment that got skipped, or steady re-exposure at school. Let’s sort out which one is happening to you.
One Untreated Head at Home Reseeds the Rest
You treated the child who was scratching. A week later a sibling starts digging at their neck, or you catch yourself doing it — and the first child has them again. It looks like the treatment quit working. It didn’t.
Lice crawl from head to head, and the person nobody checked has been carrying a quiet case the whole time. Every time you clear one child, that untreated head hands the lice right back. It’s the single most common reason a family trades the same infestation around for a month.
Wait on it and you can chase one case in circles indefinitely. The fix is to stop treating one head at a time. Check everyone under the roof the same day, and make sure everyone who tests positive gets cleared together instead of in shifts.
The Drugstore Kit Never Killed the Eggs
The shampoo seemed to work. The crawling bugs vanished for a few days, you exhaled — then a fresh batch showed up out of nowhere. That gap is the tell.
Most over-the-counter products stun or kill live lice but leave the cemented eggs alive on the hair shaft. Those eggs hatch on their own schedule, and a week later you’re back to the start. It’s exactly why so many drugstore kits leave live lice eggs behind, no matter how carefully you follow the label.
Every hatch resets the clock and lays the next round. The bottle is not the fix. What actually clears a case is pulling those eggs out strand by strand with a real metal nit comb — the step the chemicals can’t do for you.
You Skipped the Second Treatment Around Day Nine
One treatment, hair looked clear, everyone moved on. Then live lice turned up again about a week to ten days later. This one catches careful parents constantly, because the first round genuinely looked like it worked.
No single treatment kills every egg, so a second pass has to be timed for right after the stragglers hatch but before they’re old enough to lay. The American Academy of Pediatrics is specific about the window: retreatment is recommended between days 9 and 10 if live lice are seen. Miss that window and the survivors mature and start the cycle over.
Combing is the other half people drop too early. Federal health guidance is blunt about the effort involved: comb to remove nits and lice every 2-3 days, and keep it up for 2-3 weeks to be sure they’re all gone. Stopping after day two or three is how a nearly-clear head slides right back into a full case.
The Classroom Keeps Sending It Back
Sometimes you did everything right at home and it still comes back — a fresh case a couple of weeks after school starts. The source isn’t your bathroom. It’s the desk next to your child’s.
Montgomery County schools return Tuesday, August 25, 2026, and the rules have changed in a way most parents haven’t caught. Under current MCPS guidance, a child found with lice can stay in class through the end of the day and return after a first treatment, and the old send-home-for-nits rule is gone.
The county’s school health team partners with MCPS to serve over 150,000 students and manage communicable illness, but it no longer screens classrooms head by head. That means a lightly-treated or untreated classmate can quietly re-expose your cleared child, and nobody at school is checking for it.
None of that means keeping your child home. It means the watching is on you now, so it helps to know how local schools actually handle a lice case. Once school is back, run a quick check once a week — a two-minute part-line scan catches a re-exposure before it becomes another full treatment.
When to Keep Combing and When to Get Checked
Not every comeback needs a professional. Keep handling it at home when you’re only seeing a few, everyone in the house has already been treated, and you’re staying on the day-nine retreat and the every-few-days comb-out. That’s a case that’s closing, not one that’s beating you.
Get a professional check when it has come back twice, when you honestly can’t tell a live egg from a dead shell, or when the household keeps trading it no matter what you do. At that point you’re not out of effort — you’re missing a source, and a trained eye finds it fast. If you’re not sure where you stand, this is how to tell a case is truly cleared.
If you’ve been through two rounds and the lice keep returning, book a whole-family lice check at our Silver Spring clinic and we’ll find the head or the eggs the earlier tries missed.
What a Professional Clearance Actually Involves
A professional visit starts where home kits stop. We check every head in the household at one appointment, because the sibling nobody suspected is usually how a handled case walks right back in. Then we use a non-toxic, comb-based process that lifts the live lice and the eggs in a single pass, so there’s no cemented nit left waiting to hatch.
Cost is the other worry, so here’s the honest range: professional treatment here generally runs $150 to $300 per person, depending on hair length and how long the case has been building. Families travel from across Montgomery County and the DC metro for a same-day, whole-family clearance, and you can see exactly what a full professional comb-out covers before you come in.
Break the Cycle Instead of Repeating It
Lice that keep coming back aren’t a sign you failed or a sign of some super-strain. They’re a sign that one head, one batch of eggs, or one exposure slipped through — and every one of those is findable. Stop reaching for a stronger chemical and start closing the gap.
When you’re ready to end it in one visit, book a whole-family lice check and we’ll clear every head at the same time so nothing is left to reseed.
Frequently Asked Questions
Can lice really survive a full treatment?
The lice themselves usually die, but the eggs are the problem. Most treatments don’t kill every cemented egg, and the ones that survive hatch a week or so later. That’s why a case can look gone and then reappear — it’s rarely the treatment failing, and almost never true resistance.
How long after treatment should I keep checking?
Give it a solid two to three weeks. Comb through the hair every few days, retreat around day nine if you still see live lice, and do a quick part-line check weekly after that. Most comebacks happen inside that first three-week window, so that’s when your attention matters most.
Do I have to treat the whole family if only one child has lice?
Everyone should be checked the same day, and anyone with live lice or eggs should be treated together. You don’t need to dose a person who’s clear. But skipping the check is the fastest way to send the case bouncing back and forth between two heads for weeks.