The first round of lice treatment is only the beginning. What you do over the next two to three weeks determines whether the infestation is actually gone or comes back. The short version: check the hair 8 to 12 hours after treatment, comb out nits every two to three days, wash bedding and personal items in hot water, and plan for a second treatment around day nine or ten.
Check Your Results at 8 to 12 Hours
Most over-the-counter lice treatments don’t kill every louse instantly. If you see a few lice still moving slowly 8 to 12 hours after treatment, that’s normal and doesn’t mean the product failed. Those lice are dying.
What should concern you is if the lice look just as active as they did before treatment. If nothing seems to have changed at the 8-to-12-hour mark, the medication likely isn’t working. This is increasingly common. A global analysis found that permethrin effectiveness has dropped from 97% to roughly 15%, largely because an estimated 70% of head lice worldwide now carry genetic resistance to pyrethroids, the active ingredient in most drugstore treatments. If your first treatment doesn’t appear to be working, talk to your healthcare provider about a prescription option that uses a different mechanism.
Start Combing Every 2 to 3 Days
No treatment kills all nits (eggs). The ones left behind can hatch within a week, restarting the cycle. Systematic combing is the only way to physically remove them.
Here’s how to do it effectively:
- Wash hair with regular shampoo and apply a generous amount of conditioner. The conditioner makes the comb glide through without snagging and immobilizes live lice.
- Detangle first with a wide-toothed comb until it moves freely through the hair.
- Switch to a fine-toothed nit comb. Slot the teeth into the hair right at the roots so the bevelled edge lightly touches the scalp, then draw the comb all the way down to the ends.
- Check the comb after every single stroke. Wipe or rinse off anything you find before the next pass.
- Work section by section. For short hair, expect about 10 minutes. For longer hair, up to 30 minutes.
- Rinse out the conditioner, then comb through a second time to catch anything you missed.
Repeat this process every two to three days for at least two to three weeks. The term “nit-picking” exists for a reason. This step requires patience and thoroughness, but it’s the single most important thing you can do to prevent reinfestation. You’re looking for two things each session: live lice (which mean the treatment isn’t fully working) and nits close to the scalp (which could still hatch). Keep going until you find nothing on two or three consecutive sessions.
Apply the Second Treatment on Day 9 or 10
Over-the-counter treatments with pyrethrins or permethrin require a second application 9 to 10 days after the first. The timing is deliberate. Nits that survived the first round will have hatched by then, but the newly emerged lice won’t yet be old enough to lay new eggs. This window lets you kill the next generation before it reproduces.
Skip or delay this second treatment and you risk a fresh cycle of egg-laying. Mark the date on your calendar.
Wash Bedding and Personal Items
Lice can’t survive long without a human host. Adults die within two days of falling off a person, and nits usually die within a week if they’re not kept at scalp temperature. That said, a quick household cleanup on treatment day reduces the small chance of picking up a stray louse.
Focus on items that touched the head in the two days before treatment:
- Bedding, pillowcases, towels, and recently worn clothing: Wash in water at least 130°F (54°C) and dry on high heat for at least 20 minutes.
- Hairbrushes, combs, and hair accessories: Soak in hot water of at least 130°F for 5 to 10 minutes.
- Items that can’t be washed (stuffed animals, headbands, helmets): Seal them in a plastic bag and leave them for two weeks. Any lice or nits inside will die without a host well before you open the bag.
You do not need to deep-clean your entire house, fumigate rooms, or spray furniture with insecticide. Lice spread through direct head-to-head contact, not from carpets or couches. A quick vacuum of upholstered furniture and the area where the person sleeps is sufficient.
Know When Treatment Has Worked
The clearest sign of success is simple: no live, crawling lice during your combing sessions. Only retreat if you find live lice that are actively moving several days after treatment. A few dead nits stuck to the hair shaft are not a sign of failure. Nits cement themselves to hair and can remain visible for weeks or even months after they’ve died or hatched, gradually moving farther from the scalp as the hair grows.
If you’re still finding live lice after the second treatment, the product you’re using likely isn’t effective against the strain you’re dealing with. This is the point to switch approaches rather than repeat the same treatment a third time.
Sending Your Child Back to School
Both the American Academy of Pediatrics and the National Association of School Nurses recommend against “no-nit” policies, meaning a child shouldn’t be kept home simply because nits are still visible in the hair. Their reasoning is practical: many nits found more than a quarter inch from the scalp are either empty shells or unlikely to hatch, nits glued to hair shafts don’t transfer to other people, and nonmedical screenings frequently misidentify other debris as nits.
After a proper first treatment, your child can typically return to school the next day. The unnecessary days missed cause more harm to the student than the low risk of spreading lice that have already been treated. That said, check your school’s specific policy, since some districts still enforce no-nit rules despite the professional recommendations against them.
Preventing Reinfestation
The most common reason lice “come back” isn’t treatment failure. It’s re-exposure from an untreated close contact. Check all household members for lice on the same day you treat, and treat anyone who has active lice simultaneously. If only one person is treated while another family member still carries lice, they’ll pass them back and forth indefinitely.
For the weeks following treatment, avoid sharing items that contact the head: hats, helmets, hair ties, headphones, and pillows. Teach kids to avoid head-to-head contact during play, though for younger children this is easier said than done. Pulling long hair into a braid or ponytail reduces the chance of picking up lice from another child at school.