At a Glance
- Head lice resistance to common OTC ingredients such as permethrin and pyrethrins has increased over time.
- A treatment may appear to work at first even if some lice survive and return days later.
- Manual combing remains an important part of removing live lice and nits because it does not depend on chemical susceptibility.
- Signs that an OTC product may not be working include live lice remaining after treatment or returning shortly afterward.
- If the same OTC approach keeps failing, it may be time to switch to a more comprehensive removal strategy.
If you treated your child’s head lice with an over-the-counter shampoo, waited the allotted time, and then found live head lice crawling around a week later, you didn’t necessarily do anything wrong. What you may be running into is a problem that’s become more common nationwide: head lice that are resistant to the active ingredients in most drugstore treatments.
Yes, Head Lice Resistance Is a Real and Growing Problem
Over-the-counter lice shampoos that contain permethrin or pyrethrins have historically been highly effective. Studies from the 1980s and 1990s show success rates of 80% or higher. That efficacy has fallen steadily since then, and that decline isn’t due to more households misusing these products. It’s because lice populations have changed.
Research tracking this phenomenon has shown that pyrethroid resistance has steadily increased over the past decades, and meta-analyses of existing research put global resistance at 59% overall and as high as 65% against permethrin, one of the most common active ingredients in drugstore lice shampoos. Resistance rates have risen even higher in some areas, and some studies of lice in Australia, Israel, England, and Turkey have found genetic markers for resistance present in essentially the entire local lice population studied.
Not sure if a drugstore product worked? Schedule an appointment with My Hair Helpers for professional help checking for and removing head lice.
How Head Lice Become Resistant to Treatment
Head lice develop resistance through a process known as knockdown resistance. It’s a variation in how sodium channels in a louse’s nervous system work, made possible by mutations that allow the louse to better survive the onslaught of chemical treatment.
Permethrin and pyrethrins in common lice shampoos work by keeping those sodium channels open too long in the nervous system. This ends up paralyzing and killing the louse. Resistance makes those same channels act a little differently, so the chemical can’t do its job.
Lice reproduce so quickly (a female can lay up to ten eggs a day) that the trait spreads rapidly through any given population. Each time a family misses the mark or tries an over-the-counter treatment repeatedly, any remaining, drug-resistant lice get the chance to reproduce, passing their trait to the next generation. This process over decades has driven down the effectiveness of chemical-only approaches to lice treatment.
When Treatment Seems to Work, But Head Lice Return
The result, unfortunately, is that many families end up experiencing a familiar pattern: a product is used exactly as directed, no live lice are found immediately afterwards, and then a week or two later, the live lice are back. This isn’t necessarily a sign that the family has been reinfested, but rather that their initial chemical treatment may not have actually fully worked in the first place, because some of the lice survived.
Additionally, even when an effective chemical treatment kills the lice, it’s almost always less effective against nits, which lice cement onto the hair shaft. Nits are designed specifically to protect lice eggs from chemical treatment. That’s why most over-the-counter lice treatment bottles come with a second dose that should be used a week to ten days after the initial treatment.
How Manual Removal Is Still a Key Piece of a Complete Approach
A thorough manual combing treatment—using a head lice comb to carefully remove any remaining viable lice and any eggs, or nits—shouldn’t be used as an “oh well” backup plan if a chemical approach doesn’t work. Instead, it’s a crucial part of a comprehensive and effective treatment plan from the beginning, because a manual approach doesn’t depend on a chemical mechanism overcoming a resistance mutation.
A comprehensive treatment plan, as we use at My Hair Helpers, combines an effective, non-toxic treatment that’s formulated for this purpose with a nit- and lice-removing procedure that’s performed by trained professionals. So, whether or not resistance is present, the lice and eggs are physically removed.
Prefer to handle head lice at home? Shop My Hair Helpers products online for tools designed to support a thorough DIY approach.
What a Complete Head Lice Treatment Strategy Looks Like
Because of the reality of resistance, an effective approach offered by the professionals at My Hair Helpers includes both a professional treatment and a manual treatment that physically removes lice and nits, rather than relying on a chemical ingredient to do that work for you.
This is also why one or more repeated applications of the same chemical treatment often don’t do the job. If resistance is part of the problem, those same lice will survive whatever treatment you throw at them a second time. That’s why our comprehensive approach has success rates that can’t be matched by repeating the same chemical treatments.
Here’s a step-by-step look at what our process involves, whether you visit one of our salons, schedule a home appointment, or purchase our products online for a DIY approach.
- Step 1: Massage My Lice Removal Oil or My Cocomint Oil onto a dry scalp and thoroughly saturate the hair. The ingredients work by trapping and slowing down the bugs.
- Step 2: Add a few spritzes of Mint Conditioner to a spray bottle filled with water. Apply the mixture to the hair and comb through with a wide-tooth comb.
- Step 3: Section the hair horizontally from the bottom up and apply a layer of My Natural Enzymes directly to the scalp, making sure the hair is fully saturated. Leave it on for five minutes, then add another layer. Do not rinse.
- Step 4: Section the hair from ear to ear. Using a lice comb, comb through each section in all four directions, wiping the comb on a paper towel after each pass. Continue until the swipes come back clear.
- Step 5: In the morning, wash the hair with My Clarifying Shampoo or My Mint Shampoo, then use My Mint Conditioner to help restore natural luster. Repeat the process again in about a week.
Signs Drugstore Head Lice Treatment May Not Be Working
A few signs may suggest that the head lice you’re dealing with are resistant to treatment:
- Live lice remain on the scalp after using an OTC product as directed
- Live lice return within a few days of treatment rather than after a longer period that may suggest reinfestation
- Repeated attempts fail to fully resolve the infestation despite following the product directions carefully
Of course, this doesn’t mean that you or your kids did anything wrong in the process, just that your family may need a different approach than what you’ve been able to get out of the OTC product.
Don’t Keep Fighting Head Lice the Same Way
If drugstore products don’t seem to be working, it doesn’t mean you’re doing anything wrong. Head lice can be persistent, and treatment resistance may be part of the reason. The key is knowing when to stop repeating the same approach and try something different.
My Hair Helpers offers salon appointments, mobile services, and at-home products to help families take the next step with a more thorough plan. Find a pathway that works for you and get rid of stubborn head lice for good.
Frequently Asked Questions About Head Lice Resistance
How can I tell if the head lice on my child are resistant, or if I just used the product wrong?
It can be tough to tell the difference between using the product wrong and dealing with resistant head lice. But, if you carefully followed the instructions and used enough of the product, and then you still found live lice afterward, resistance is worth considering.
Are all-natural or botanical head lice shampoos more effective if resistance is a concern?
Not all botanical and all-natural head lice shampoos have the same effectiveness. Switching to a different OTC shampoo isn’t enough in and of itself to deal with resistance, especially if manual removal doesn’t happen. The most reliable approach combines a professional, effective treatment with manual combing.
Can resistance develop to the professional treatments used at places like My Hair Helpers?
Resistance is unlikely to develop to the professional treatments used at places like My Hair Helpers. Our treatment formulas are different enough that they don’t contain the same chemical ingredients and won’t create the same selective pressures that put you at risk of resistance.
Should I keep retrying an OTC lice shampoo?
Repeating a failed OTC treatment doesn’t do anything more than leave your family still fighting a stubborn infestation, just like waiting too long to treat your head lice.
Is manual nit combing still necessary if resistance is an issue?
Manual nit combing is still necessary if resistance is an issue. This step physically removes lice and nits from your scalp and hair, and isn’t dependent on a chemical mechanism overcoming a resistant gene. So whether or not a given lice population has become resistant, manual combing can make all the difference.
