How To Get Rid Of (Resistant) Head Lice

We’ve conquered polio and smallpox. We’ve put a man on the moon and explored the depths of the oceans. We’ve mapped the known universe and the human genome. Yet we still haven’t found a way to get rid of head lice.

In fact, head lice are actually getting tougher (they’re becoming increasingly resistant to common treatments) and thus less susceptible to treatment.

Experts put the prevalence of louse infestation down to three factors:

  • ineffective treatment,
  • incorrect use of treatment,
  • and headlice gaining resistance to insecticides.

Head lice mutate quickly because of their fast reproductive cycles (a female can lay an egg every 4 hours).

And if a single resistant louse survives after treatment they will go on to found an entire generation of hard-to-kill offspring.

Although we’ve moved on from the days when any child found to have lice was shaved by the school nurse or sprayed with DDT, many schools have “no-nit” policies which ban children from attending until they are clear.

delousing people by spraying their heads with DDT was an effective treatment
back in the day, delousing people by spraying their heads with DDT was a common treatment

The ‘no nit policy’ is a pretty extreme reaction to a problem which the American Academy of Pediatrics (AAP) says is entirely harmless. (source: PubMed.)

Unlike body lice or fleas, head lice do not carry disease, and they aren’t a sign of a dirty home; the worst risk is irritating your scalp by scratching too hard.

For that reason, the AAP says that harsh treatments should only be a last resort. Let’s look at some of the most common treatments for head lice, and evaluate their effectiveness.

Head lice treatments that work

(and a few that don’t)


Wet combing

This is the backbone of any lice treatment regimen. The big advantage of wet combing is that lice can never develop resistance to it.

  • Separate the hair into sections,
  • comb it through with a very fine-toothed comb,
  • and wipe the comb after every stroke to get rid of anything you’ve picked up.

Coating the hair with something greasy (like hair oil or conditioner) will make combing easier, but the idea that it also stops the lice from gripping on to the hair is an old wives’ tale.

If you have the patience, wet combing alone will get rid of lice, although it needs to be repeated every couple of days to catch lice which have hatched from missed eggs.

Head louse eggs take 7-10 days to hatch, but of course not all the eggs in your hair will have been laid at the same time.

By combing every couple of days, you’ll pick up every new “batch” of lice when they hatch.

Lice combs


Metal combs are much more effective than plastic. Metal combs have tines so close together that hair can pass through but lice eggs get tugged out; plastic combs pull out live lice but usually can’t get the tiny eggs. They are also more durable than plastic combs, especially in case of thick hair.

Some metal combs, such as the nit free Terminator lice comb and the Lice Lifters Nit Removal Comb sport micro-grooved teeth.

Because of the micro spirals around the teeth these combs are able to effectively grip eggs and lice, thus pulling them from the hair.

Lice zapping combs

If you’re getting tired of wet combing, electronic louse combs provide such a an alternative.

Used on dry hair, lice zapping combs such as the Robi comb or Lice Guard generate a mild electronic current through their metal tines, so that any louse they pick up gets electrocuted.

While they aren’t any more effective than regular louse combs, the buzzing and zapping can make them fun for children who hate wet combing.

Suction combs such as the V-comb

These devices employ a rounded, stainless steel-toothed comb in combination with suction power to gently lift eggs and lice from the hair and scalp.

Basically, the V-comb combs and simultaneously vacuums nits and lice out.

 

Over-the-counter remedies


Most over-the-counter (OTC) remedies are neurotoxins, which poison the lice in the same way that pesticides kill insects.

There are a few alcohol-based ones coming onto the market, which work by melting the exoskeleton of the lice.

Do you need to worry about putting such strong chemicals on your skin?

In fact, the bigger risk is that many OTC treatments don’t work, meaning you might have to try three or four different neurotoxins before you find one which clears the infestation.

Efficacy more important than toxicity?

In some areas, lice have grown entirely resistant to a certain type of treatment, and many physicians prescribe a different treatment every few months in order to prevent local louse populations from developing resistance.

Pyrethrin and Permethrin are the two most common active ingredients in OTC louse treatments.

  • Pyrethrin is derived from chrysanthemum plants, which secrete a type of natural insecticide,
  • and permethrin is an artificial version.

Although both were highly effective when they were introduced in the 1970s, decades of use have allowed lice to build up resistance to the point that one medical review described the substances as “not sufficiently effective to justify their use”.  Various public health organizations advice against using these agents.

  • Shampoos containing pyrethrins and a substance called piperonyl butoxide (a popular brand is Rid shampoo, spray, or the RID Complete Lice Elimination Kit ) are still recommended by for instance, WebMD.
  • Also permethrin creme rinse 1% (i.e. Nix), is generally accepted as a first choice for treating head lice.

Isopropyl myristate is alcohol-based and works by destroying the louse’s exoskeleton. In theory, this physical effect it’s impossible for lice to develop resistance.

There are easy-to-use commercial treatments such as Full Marks solution, available, but you can also buy bottles of isopropyl myristate online since the chemical is widely used in cosmetics.

Non-toxic OTC lice treatment products


LiceMD

Is a popular head lice product that does not contain toxic chemical or harsh pesticides. It helps you get rid of lice yet does not kill lice eggs so it needs to be combined with a lot of combing.

Follow the instructions closely and this 4% dimethicone (dimeticone) solution offers a toxin-free way to get rid of head lice. LiceMD is sold in the UK as Hedlin)

 

Licefreee Spray

Don’t be fooled. Its active ingredients may sound very technical but this product basically contains table salt. Yet both reviews as well as research show it works and is safe.

Licefreee spray with natrum muriaticum and sodium chloride is an all-natural, highly popular alternative to harsh products.

If you’re on a budget you may want to try the table salt from your kitchen cabinet first. Read on to learn more.

Natural remedies


OTC remedies with natural ingredients vary widely. Some have been proven to be as effective as prescription medication; others are basically useless.

Since there are hundreds of different treatments available, the best way to evaluate their usefulness is by looking at the ingredients list and seeing whether it uses some of the effective natural ingredients discussed below.

Head lice are tough little suckers and it takes a lot to kill them. For that reason, natural treatments are often just as harsh as the stuff you get from the drug store.

For instance, gram for gram, tea tree oil is significantly more toxic to humans than the prescription-only insecticide malathion.

Oils and suffocation-based treatments

A common home remedy is to apply suffocating agents like olive oil, hair gel, melted butter, or conditioner, in the belief that they will stop the lice breathing.

You will need to apply liberally and leave it on for at least 12 hours, since head lice can live for a long time without air.

  • A common treatment is to smear the hair with oil, wrap it in a shower cap and leave it on overnight, then comb out the lice with a fine-toothed comb in the morning.

There are suffocation-based lotions which are applied to the hair then dried on with a hairdryer. The cream goes on in a thick layer then contracts when it dries, which ‘shrink-wraps’ the lice so they are crushed.

Treatments like these are effective at killing live lice but do not affect the eggs, so remission is inevitable unless you do something else to get rid of the eggs.

Coconut oil

If you leave it on for long enough, any oil will eventually kill head lice by suffocation. But coconut oil is toxic to head lice after just a short application.

In laboratory tests, hair was saturated in coconut oil then washed clean after 20 minutes; 80% of lice were dead within 4 hours.

Another study found it was as effective as the insecticide DEET in killing head lice.

Smelly substances


Some people swear by using pungent treatments like garlic, chili, or sesame oil, claiming that the strong smell will suffocate the lice.

Lice ‘breathe’ by absorbing oxygen through their skin; there’s no way you can choke them to death with bad smells.

Acidic treatments


Head lice are sensitive to acid, since the hard shell of their eggs softens when it comes into contact with anything acidic.

Vinegar

Acetic acid (5% concentration) and formic acid (8% concentration) have both been proven to help dislodge eggs, but they don’t have much effect on live lice.

Acetic acid is just the chemical term for vinegar, which has long been used as a home remedy for head lice.

Experiments suggest that vinegar will be most effective if you use it to soak the hair after treatment and then comb through while your hair is still wet with vinegar.

That way, the acetic acid will help to loosen the egg sacs so the comb can dislodge them.

Mayonnaise

Mayonnaise is a popular home remedy despite having never been tested in a lab. Like any oil-based substance, it will eventually suffocate the lice if you leave it in the hair for long enough.

Since it also contains vinegar, it’s likely to work a bit better than other suffocation-based treatments like petroleum jelly or hair conditioner.

If nothing else, the mayonnaise will make your hair beautifully soft and perhaps curly.

Acidic shampoo

There’s also some evidence that washing with acidic shampoo (with a pH of 4.5 to 5.5) before wet combing can make it easier to dislodge eggs, since it softens their outer shell.

You can find lists of acidic shampoos online, which can be handy as most manufacturers don’t publicize the pH values of their shampoo unless you contact them directly.

Dehydrating treatments


Some treatments work by dessicating the lice, rather than poisoning them. The beauty of these treatments is that there’s no way for a louse to develop resistance to being dehydrated.

Table salt

One effective natural treatment is based on sodium chloride (table salt) at a 1% concentration. Leave the salt spray in your hair overnight, and the lice will be shrivelled and dead when you shampoo it out in the morning.

If you’re lucky enough to live by the beach, then swimming in sea water without rinsing your hair afterwards is likely to have a similar effect.

Alcohol

An old-fashioned treatment is to daub the roots of your hair with methylated spirits or another neat alcohol.

Alcohol is a powerful dehydrating agent; the lice and eggs will shrivel like raisins. Your scalp will also feel dry and tight afterwards, but your skin will quickly recover and the lice won’t.

Saponin

Saponin is a soap-like substance which can be extracted plants like yucca. It’s often used in natural detergent brands, and some natural lice treatments are based on yucca extract.

According to studies, saponin kills lice by turning the protoplasm inside them (the equivalent of blood in a human) into a solid rather than a liquid.

Essential oils


Essential oils are often recommended as a natural treatment for head lice. Some of them work; others will just make your hair smell lovely without dislodging the lice.

The key is the chemical nerolidol, a natural insecticide with a citrus smell. Lavender, ginger, jasmine, and tea tree plants all produce nerolidol as a way to repel pests, and the chemical survives after the plants are processed into oils.

Both lavender oil and tea tree oil have been proven highly effective against head lice, with a solution of tea tree oil at 8% concentration killing every single louse in a lab test.

Not every oil has been tested, but it’s likely that other substances with a high concentration of nerolidol will have similar effects.

Remember that essential oils, although natural, still contain powerful chemicals and can irritate the skin just as much as harsh pesticides. Tea tree oil is poisonous if ingested and must be used with care.

Nitpicking


is what we used to do before louse combs were cheap and widely available. Some people still pick out lice with their fingers because it’s what was done for them as children.

Aside from the time and trouble it takes, it’s ineffective because you will only be able to pick out large adult lice, not eggs or nymphs (recently hatched lice.)

Unusual treatments


Shaving

Shaving your hair off is what would traditionally happen if you were found to have head lice at school or in prison. It’s the most extreme measure you can take but it definitely works.

Hair dying

While it’s not exactly recommended by doctors, anecdotal reports suggest that dying or bleaching your hair will kill a louse infestation immediately.

The chemicals in dye are powerful enough to strip the color from your hair, so it makes sense that they would poison lice and eggs.

Hairdryer

Surprisingly, you might already be using a powerful anti-louse treatment every time you wash your hair: your hairdryer.

Blowdrying can kill a massive 98% of eggs, but you need to use the right technique for it to be effective:

  • work on already-dry hair (otherwise the eggs will stay damp),
  • divide the hair into thin sections,
  • and target the roots with an airflow which is strong but not too hot. More instructions here.

Since live lice can run away from the blast, this technique is most effective when it’s used in conjunction with another treatment – remembering that some chemical treatments are flammable and you should keep away from sources of heat after using them.

There are also specially-designed blowdrying tools such as the AirAllé professional lice device which claim to kill a high proportion of live lice as well as eggs.

 

No-hassle treatments


Hire a de-louser

In some areas, it’s possible to hire a professional de-louser to come to your home. They use the same treatments that anyone could use, but they save time and trouble.

These services can be a godsend if you’re a busy parent, because it saves you having to spend a tedious evening combing through your childrens’ hair.

mThe downside, of course, is the cost.

Also, keep in mind that certain de-lousing companies will pressure you to pay extra for unnecessary “sterilizing” treatments, like steam-cleaning furniture or treating family pets.

Prescription-only remedies


These can only be issued by a doctor and are recommended only when OTC treatments have repeatedly failed.

Malathion is an insecticide to which lice show little resistance. It kills permethrin resistant human head lice ten times faster than Nix or permethrin and should not be used by women who are pregnant or breast-feeding. (source: PubMed.)

Spinosad topical suspension is a newer prescription treatment for head lice, and since it was introduced in 2011 there have been no reported cases of resistance.

  • Possible side effects include redness or irritation of the eyes and skin, and the medication isn’t recommended for children younger than age 4.

Ivermectin can be used as a single-use lotion or taken orally. Research shows the oral treatment is highly effective and is the most common “last resort” treatment in the USA.

Benzyl alcohol lotion works in a similar way to isopropyl myristate, but is available on prescription only since it has more potential side-effects.

Finally, lindane is a topical treatment which has been banned in the EU as a dangerous carcinogen. It is still occasionally prescribed in the USA, where the Food and Drug Adminstration resisted calls for a ban.

Preventing Re-infection


Now you’ve got rid of the infestation, how do you keep clear?

Firstly, it’s important to keep wet-combing your hair for a couple of weeks, even after you think the infestation has gone away.

Often, people think they have been re-infected, when actually they just missed a couple of eggs which have now hatched into a renewed problem.

It’s common advice to sterilize everything that could have touched your head – brushes, pillowcases, towels, hats… Though it might make you feel better to wash everything in hot water, there’s no medical reason to do so. (in case of body lice there is.)

A less tedious solution is offered by lice treatment sprays for clothes, bedding, hats and other belongings. A well-reviewed product is Eco Defense Lice Protection.

However, whether such treatments are a necessity remains to be seen.

It’s theoretically possible for a louse to walk onto a scarf and then climb back onto your head later, but the risk is incredibly low: lice need to eat so regularly that they will die after 24 hours away from a human head.

Eggs are securely anchored to the hair shaft and there’s no way that they can fall out.

Hair tied back, no hugging, space out belongings which may have touched the head (e.g. hats and scarves on racks at school).

Some schools have “no-nits” policies and won’t allow either children or staff to come in if they have an infestation: this makes a lot of trouble for parents without preventing the spread of lice.

Lice can only be transferred by direct hair-to-hair contact. (There’s also a tiny risk of lice being transferred by sharing things like hats or towels, but it’s pretty unlikely.)

For that reason, the best way to prevent re-infection is just to keep your head away from others’. Stay away from hugging, close personal contact, and crowded subway rides.

One more thing..

Empty egg cases may remain glued to the hair for up to 6 months after successful treatment . Because of this, some people see the sticky egg cases from a long-ago infestation and think the head lice have come back.

 

References

Prevention and treatment of head lice in children. PubMed.gov.

Yucca-based lice treatment. Zapping Head Lice – Chicago Tribune.

Historical photo of delousing with DDT. Pinterest.

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