To kill head lice, you need a treatment that targets both live lice and their eggs (nits), applied at least twice over a period of 7 to 10 days. A single treatment won’t do it because most products can’t kill the newest eggs, so a second round catches nymphs that hatch after the first application. Your options range from over-the-counter products and prescription treatments to manual removal with a fine-toothed comb.
Confirm It’s Actually Lice First
Before you start any treatment, make sure you’re dealing with lice and not dandruff, dry skin flakes, or hair product residue. The key difference: nits are glued to the hair shaft and don’t slide off easily. Dandruff and other debris slide freely when you pinch and pull along the strand. Nits are tiny, oval, and often yellowish-brown near the scalp (turning white once hatched). Live adult lice are about the size of a sesame seed, tan or grayish-white, and move quickly away from light.
Look behind the ears and along the nape of the neck, where lice prefer to lay eggs. Using a fine-toothed nit comb on wet, conditioned hair is the most reliable way to find them.
Why Over-the-Counter Products Often Fail
The most common drugstore lice treatments contain permethrin or pyrethrins. These work by paralyzing the lice’s nervous system. The problem is that lice have been developing resistance to these chemicals for decades. A systematic review of global data found that roughly 77% of head lice now carry genetic resistance to pyrethroid-based products. In some countries, including Australia, England, Israel, and Turkey, resistance rates hit 100%, making these products essentially useless.
This doesn’t mean OTC treatments never work, but if you apply a permethrin-based product like Nix and still see live lice crawling 8 to 12 hours later, resistance is the likely explanation. Don’t keep reapplying the same product hoping for better results. Switch to a different approach.
Treatments That Work Better
If OTC pyrethroids fail, several alternatives have stronger evidence behind them.
Dimethicone-Based Products
These silicone-based treatments kill lice physically rather than chemically. They coat the lice and seal off the tiny breathing holes along their bodies, suffocating them. Because this is a physical mechanism, lice can’t develop resistance to it the way they do with insecticides. Dimethicone products are widely available without a prescription in many countries and are a good first-line option if you suspect resistance in your area.
Prescription Options
Spinosad (brand name Natroba) is a naturally derived treatment that disrupts the lice’s nervous system through a different pathway than pyrethrins. In two large clinical trials comparing spinosad to permethrin, 85 to 87% of people treated with spinosad were lice-free, compared to only 43 to 45% with permethrin. A major advantage: spinosad kills lice effectively enough that nit combing isn’t required for it to work, though combing still helps.
Ivermectin, available as both a topical lotion and an oral tablet, causes paralysis in lice by a completely different mechanism than pyrethroids. Malathion lotion is another prescription alternative that works as a nerve agent against lice. Both require a second treatment in seven days if live lice are still present.
The Wet Combing Method
If you want to avoid chemicals entirely, systematic wet combing can clear an infestation on its own. The method requires patience and consistency, but it works. In studies comparing wet combing to chemical treatment, cure rates were comparable when the method was followed correctly.
Here’s the process: apply a generous amount of regular hair conditioner to wet hair. The conditioner immobilizes live lice and makes the hair slippery enough for a fine-toothed nit comb to glide through. Comb through the entire head in systematic sections from root to tip, wiping the comb on a white paper towel after each stroke so you can see what you’re removing.
The schedule that matters most:
- Day 1: First combing session
- Day 4 or 5: Second session
- Day 9 or 10: Third session
- Day 14: Final session and check
This schedule is spaced to catch newly hatched nymphs before they’re old enough to lay eggs themselves. Skipping a session or stopping early is the most common reason wet combing fails. When applied consistently, about two-thirds of cases clear with this method alone.
The Two-Treatment Rule
Whatever method you choose, plan for at least two rounds. Lice eggs take about 7 to 10 days to hatch. Most treatments, even effective ones, don’t reliably kill all eggs. The second treatment, timed 7 to 10 days after the first, catches nymphs that hatched from surviving eggs before they mature enough to reproduce.
The specific timing depends on your product. Permethrin-based treatments call for retreatment at 9 to 10 days. Spinosad and malathion recommend a repeat at 7 days, but only if you still see live lice. Skipping that second treatment is one of the most common reasons infestations come back.
What About Home Remedies?
Mayonnaise, olive oil, coconut oil, and petroleum jelly are all commonly suggested as suffocation treatments. The idea is that coating the hair and scalp in a thick substance blocks the lice’s ability to breathe. There’s some truth to it, but the evidence is underwhelming. These substances can kill a significant number of lice only when applied in large quantities and left on for more than 12 hours, typically overnight under a shower cap.
Even then, they rarely kill all the lice in a single session, and they do very little to eggs. If you go this route, you’ll still need to comb out nits and repeat multiple times. For most people, a proven OTC or prescription product combined with thorough combing is faster and more reliable.
Cleaning Your Home and Belongings
Lice can’t survive long off a human head. They need blood meals every few hours and typically die within one to two days without a host. That said, a few simple steps prevent reinfestation from bedding or clothing.
Wash sheets, pillowcases, and any recently worn hats, scarves, or coats in hot water above 130°F, then run them through a hot dryer cycle. Soak combs, brushes, and hair accessories in water of at least 130°F for 10 minutes. For items you can’t wash, seal them in a plastic bag for two weeks. The lice and any hatching nymphs will die without access to a host.
You don’t need to deep-clean your entire house, fumigate rooms, or throw away furniture. Lice spread almost exclusively through direct head-to-head contact, not from the environment. Focus your energy on treating the hair thoroughly and doing a second treatment on schedule.
Choosing the Right Approach for Children
Most lice cases occur in kids between ages 3 and 11. Permethrin-based products are approved for children as young as 2 months, making them a common starting point. If those fail, prescription options like spinosad are approved for children 6 months and older.
Wet combing is safe at any age and avoids chemical exposure entirely. For very young children or those with sensitive skin, it’s often the best first option. The main challenge is getting a small child to sit still for 20 to 30 minutes of careful combing every few days for two weeks. Having a favorite show or tablet ready makes a real difference.