Head lice are a fact of life and many effective treatments are available to both treat and prevent infestations. Although they can seem difficult to eradicate, and appear to keep coming back, it just takes perseverance to break their life cycle of these lice. I’ve reviewed what I believe are the best head lice treatments below, including the right ways to wet and dry comb to dislodge these little pests.
Infestation is nothing to be ashamed of and does not reflect your family’s level of hygiene – tests show that head lice actually prefer living in clean rather than dirty hair. They have co-existed with us throughout human history, have been identified on Ancient Egyptian mummies, and are the source of many common phrases such as ‘feeling lousy’, nit-picking, nitty-gritty, calling someone a Nitwit and going through things ‘with a fine tooth-comb’.
Head lice have even helped in the election of public dignitaries. In medieval Sweden, candidates hoping to become Mayor of Gothenburg supposedly sat round a table with their beards resting on top. A head louse was placed in the centre of the table and, as lice were believed to find virile men the most attractive, the owner of the thatch into which the louse crawled was elevated to the status of Mayor.
Just the thought of head lice and nits will trigger a primitive urge to itch – I’m scratching even as I write this – and if you aren’t itching by the time you finish this article I will be impressed.
What are head lice?
Head lice (Pediculus humanus capitis) are small, blood-sucking, wingless insects, that live on scalp hairs and resemble the size and colour of sesame seeds.
Infestation is most commonly seen among children aged 5 to 11 years, but they can infest anyone of any age – even grandparents. They tend to prefer girls rather than boys, but this appears to relate to hair length, sharing hair brushes and hair bands, and ease of spread, rather than any hormonal or scent preferences, or survival advantage.
Symptoms of head lice infestation
Head lice feed exclusively on human blood, every four to six hours, during which they produce small amounts of saliva. This can trigger a hypersensitivity reaction to cause itching – but not usually until 4 to 6 weeks after the infestation starts. Even then, only one in three children develop this symptom, so don’t assume someone is not infested just because they don’t itch.
When itching and scratching do occur, symptoms are usually worse behind the ears and at the back of the neck. You may also notice tiny, red, inflamed bites on the scalp or a rash on the back of the neck or behind the ears.
Yellow staining of shirt collars is a good give-away sign, as are black specks (digested blood) on collars and pillows.
How head lice multiply
Head lice have been described as mechanised dandruff. They hang around on hair shafts, nibbling blood and rarely travel far for the toilet.
They swing from hair to hair, meeting members of the opposite sex and, after reproduction, the males get back to sucking blood (and flirting with other females) while the fertilised ladies start laying eggs.
A female head louse only has to mate once during her life and stores sperm in a special tube, squeezing them out when needed; it therefore only takes one fertilised female to start a new infestation on a clean scalp. Each female has two ovaries, each with 5 smaller ovarioles, each of which carries 2 to 3 developed eggs at any one time.
A mature female will lay 5 to 10 eggs every night. These oval egg capsules, commonly known as nits, are each stuck to a single hair, close to the scalp for warmth, using the insect equivalent of super glue. This glue has a similar amino acid composition to human hair, so designing a product to just dissolve the glue without harming your hair is not an easy option.
An adult female lays up to 300 eggs before it dies, around 30 days after reaching adulthood. The average host carries around 20 adult female lice which, if left untreated, can multiply to a host of 5000 lice or more within just a few months. It is the sheer number of eggs produced that can make an infestation so difficult to eradicate.
Fresh lice eggs are protected by a hard shell which can range from brown to pale yellow or even white. They blend in easily with hair colour and are often difficult to spot.
Incubated by the hosts’s warmth, the lice eggs hatch after 7-10 days, leaving behind an empty, pale case which is commonly referred to as a nit.
Newly hatched lice (nymphs) take 12 days to reach adulthood, shedding their outer shell three times as they grow.
Adults are 2-4 mm long, with females being the largest, and vary in colour from pale tan to dark brown, often adapting to resemble your hair colour.
How do you catch head lice?
Head lice are wingless and can’t fly. They usually pass from head to head during direct hair-to-hair contact and are programmed to search out new mates which, unlike those on their current head, are not directly related to them. They take any opportunity to pass from head to head, clambering across a ‘bridge’ of hair using their six, clawed legs rather like grappling hooks. Lice only need contact with a single head hair to grab on and swing aboard.
Head lice can move fast, too, with young adults travelling a rate of 23 centimetres or more per minute – the higher the temperature, the faster they move, which is why infestations tend to spread more quickly during warm weather.
Although they were traditionally thought to only pass from person to person through direct hair-to-hair contact, researchers were intrigued by a head lice epidemic in an elementary school epidemic in the United States in which 17 teachers were infested yet all denied head-to-head contact with any students or fellow teachers.
They investigated and found that, when a head louse senses a potential danger such as bright light, an unpleasant odour (including lice repellents) or hair agitation (brushing, combing or a scratching finger), they either race back towards the scalp for safety, or transfer to the end of hair shaft ready to drop off if evacuation proves necessary. Researchers have dubbed this hopping off reaction the ‘flee response’ although the ‘flea response’ may be more appropriate. Lice drop off onto the shoulders during brushing or combing and when the investigators agitated the hair of infested people they found lice on themselves even through they were careful to avoid hair-to-hair contact.
They also found that dry combing can build up enough static electricity to eject an adult louse more than a metre away from the scalp, and that young nymphs are light enough to be blown around in the air. This is thought to be one way in which transmission of head lice occurs within nurseries and schools.
Head lice survive away from the body
An adult louse can live for at least 36 hours, and up to 3 days, away from the human scalp without feeding on a nice, warm blood meal. With optimum temperature and humidity, the eggs (nits) can survive and hatch after 10 days away from a host.
Lice deposited on brushes, combs, helmets, hats, cushions, bedding or towels therefore have plenty of time to find a new host when the contaminated brush, pillow or hat is used by someone else.
Lice are easily transferred from wet hair to a towel and can walk across linens, clothing, carpets and even attach to human hands and arm hairs without difficulty. One study found the incidence of lice on pillowcases was 4% per night. As pillowcases can pose a risk for re-infection after treatment, consider placing them in a hot tumble-dryer for 15 minutes, or wash them at 60 degrees C or higher, which will kill them.
Using a hair dryer also consistently dislodges head lice, at high and low speed settings.
Although head lice can survive immersion in the chlorinated water of swimming pools, this is not thought to be a common form of transmission.
Detecting head lice
The gold–standard for diagnosing head lice is seeing live lice or nits (egg cases) clinging to hairs. To spot these, look along the nape of the neck and in the hairline behind the ears in a good light. A magnifying glass is helpful. Look for tiny insects clinging to hairs, and oval, dark (live) or pale (hatched) egg cases stuck to hairs.
As the hair grows, old egg cases move further up the shaft providing a good indication of how long infestation has been present – nits found 1cm from the scalp suggests infestation for one month, 2cm suggests 2 months and so on.
As lice are so small, and quickly move away from areas of disturbance, visual inspection is not fool-proof – especially as they can adapt their colour to the surrounding hair.
Similarly, dandruff and the bulbs of dead hairs are easily mistaken for nits. The cheapest method of detection is to use a fine-toothed, bug-buster lice/nit comb on wet, slippery, well-conditioned hair, and to look for lice within the comb.
How to treat head lice
The traditional way to remove lice was to pick them out with your fingers. Using a fine comb is more effective as this dislodges the louse’s grip on a hair. Wet combing with conditioner and a fine-toothed comb can remove newly hatched lice and nits.
Usual advice is to repeat mechanical and natural treatments at least four times, several days apart (eg days 0, 3, 7, 10 and 14) to remove all newly-hatched lice before they mature enough to reproduce. All family members with head lice should be treated on the same days to avoid re-infestation.
Brisk brushing, twice a day, with an old-fashioned bristly brush (plastic and spiky ones don’t work) can also help. This knocks the legs off lice so they cannot hold on, or feed.
Wet combing to remove head lice
Lice close their breathing tubes (spiracles) when they are wet and lie very still to conserve oxygen. This makes them easier to detect and comb out. After shampooing and conditioning the hair, place a white towel around the child’s shoulders, and comb out any tangles with an ordinary comb. Then apply a little more conditioner (or one of the natural treatments mentioned below).
Divide the hair into sections and carefully pass the lice comb through each section, starting at the scalp and running through to the hair tips. After each stroke, wipe the comb on a tissue and look closely for live lice.
If lice are present, carry on combing hair for at least 30 minutes (eg while watching TV) and repeat every 3 to 4 days, for two weeks, to remove newly hatched lice and nits. This must be repeated every 3 to 4 days, for at least two weeks. It is effective in almost 60% of cases but you only have to miss one fertilised adult female for the infestation to start again.
I found the most effective method was to get my kids to kneel with their wet hair over the bath, so I could comb away from their scalp, and myself, to dislodge lice directly into the bath. This also made the lice easy to see against the white bath and the kids joined in the fun by shouting out the number we dislodged.
When screening hair, comb each area at least three times. If, after combing thoroughly, you are certain no lice are present, rinse excess conditioner from the hair (unless using a leave-in product) and dry as normal.
This approach alone works in around a third of cases, but is time-consuming and risks spreading infestation to the comber, too. You only have to miss one fertilised adult female for the infestation to start all over again. This may seem like the child has been reinfected, but in reality, reappearance of lice often represents a treatment failure.
Research suggests that using a bug busting kit alone can eradicate lice in 57% of cases. When you combine wet combing with a neem oil shampoo and leave-in conditioner, the effectiveness of treatment greatly increases, with all lice and eggs killed after ten minutes exposure.
Nit combs can be used alone with conditioner for wet combing, or with anti-lice treatments.
Dry combing with an electronic comb to remove head lice
Dry combing risks spreading head lice during their ‘flee response’ but this is avoided if you use an electrified comb. The low-level electricity (1.5v) paralyses or kills lice without affecting or harming you (although this method is not recommended for people with epilepsy, heart failure or with a pace-maker fitted).
These electronic nit combs usually have two settings: a lice identification mode which buzzes when a stunned louse forms a connection across the teeth of the comb, and a higher lice elimination mode for killing and treating and infestation.
Electronic head lice combs will seem familiar to any female who epilates her legs, as it is based on similar technology. They make detecting and killing head lice an easy and satisfying task.
NB Do not use electrified combs on wet hair.
Neem seed oil kills and repels head lice
Neem seed oil is a natural, plant-based insecticide that helps to immobilise head lice, making them easier to remove during combing.
In one study, an anti-louse shampoo containing neem seed extract was used on 12 children with an intense infestation of head lice. After ten minutes exposure, no head lice survived and at least 50 to 70 dead lice were combed from each child’s hair after rinsing with tap water.
The next step was to see whether eggs could survive this treatment. Eggs (nits) from both head and body lice were incubated in a shampoo containing neem seed extract for 5 to 45 minutes. In fact, it only took 5 minutes exposure for the neem seed shampoo to stop any eggs from hatching (76% of untreated control eggs did hatch).
The neem-based shampoo was found to block the egg air holes (aeropyles) to prevent the larvae accessing oxygen and causing a build-up of poisonous carbon dioxide.
For absolute certainty, I recommend leaving a neem-containing shampoo on the hair, covered with a shower cap, for ten minutes before rinsing, applying a neem seed oil conditioner and combing with a fine-toothed comb to remove the dead head lice and nits. This approach has the potential to offer a complete cure from head lice with a single treatment. However most products recommend that you repeat the treatment after ten days to catch any lice that manage to survive and hatch.
Tumble-dry pillows and change bedding, towels, pyjamas and clothes to reduce the chance of re-infestation. It’s worth treating all family members at the same time, too, even if they don’t have symptoms (one of our grannies was surprised to find she harboured 5 little unexpected lodgers!)
Neem oil also acts as a lice repellent and helps to relieve scalp dryness and itch, too. Some neem hair products contain neem leaf extract rather than neem seed extracts (neem oil) which is fine for treating scaly scalp conditions, but less effective for killing head lice, so check labels.
Other effective non-pesticide head lice killers
Not everyone likes the smell of neem oil, and other products that kill head lice without using strong pesticides are available. These have a physical action on head lice and, rather than killing them with poison, cause them to rapidly dehydrate or block their breathing tubes so they cannot obtain oxygen and suffocate.
Salt mousse for head lice
One effective approach is to cover hair with a mousse containing a strong concentration of salt (sodium chloride) which quickly disrupts the fluid balance of lice to they dehydrate and die.
The female head louse shown here has recently fed and filled with its host’s blood. After treatment with Vamousse, the lice will have dehydrated and the dark area in the centre of its abdomen will have disrupted internally to kill the louse.
Vamousse is easy to apply. Start with dry hair, separate into sections and saturate the hair and scalp with the mousse. Wait 15 minutes then shampoo the hair as normal.
You could use a Neem oil shampoo as a double treatment.
Coconut oil is also used to block lice spiracles so they suffocate and become inactive.
Silicone for head lice
Cylcomethicone and dimeticone are silicone-based substance that block lice breathing tubes and lubricate hair so lice are easily dislodged during fine combing. These have now largely replaced the traditional olive oil treatment, which required olive oil to be left on the hair overnight. These products have a smaller molecular structure that seeps into the head lice air holes more easily to kill the lice within ten minutes.
Some silicone derivative products also contain isopropyl myristate which dissolves the outer coating of lice so they dehydrate and are unable to survive – a double-edged attack for hatched lice.
Simply apply to dry hair and massage in until the hair is completely wet. Leave for 10 minutes before combing to remove dead lice and eggs. Shampoo afterwards. Repeat after seven days to catch any eggs that survived the first treatment and have since hatched.
Full Marks Solution is widely recommended by doctors. It contains both cyclomethicone and isopropyl myristate.
Dimeticone products kill head lice in one minute and their eggs (nits) in eight hours. Leave on hair overnight for best results (covered with a shower cap).
Chemical pesticides for head lice
Over the last 20 years, head lice have built up considerable resistance to chemical insecticides. As the larvae have multiple outer shells (exoskeleton) they often survive by shedding their outermost casing to receive a sub-lethal dose. Of those used, malathion has retained the most effectiveness (78%).
However, malathion is an organophosphate that acts as a nerve toxin. It works by blocking the action of a chemical, cholinesterase, that is essential for the growth and survival of lice. Its use should be limited in children. The British National Formulary recommends malathion is only applied twice, one week apart. Some of the insecticide is absorbed into the body, but the risks of systemic side effects associated with 1 – 2 applications is considered very low. Avoid using at intervals of less than one week, and do not apply for more than 3 consecutive weeks.
Because of its potential for neurotoxicity, I don’t personally recommend malathion. The products I have reviewed above are more effective when used according to manufacturer’s instructions, and are much safer. If you do wish to use malathion, however, Derbac M liquid is available from pharmacies such as Pharmacy2u.
To prevent head lice re-infestation
- Tell the parents of your children’s best friends that head lice are around, so they can be checked and treated if necessary
- Check everyone in your family
- Start brushing hair thoroughly twice a day
- Discourage children from close head contact with others
- Avoid sharing items such as brushes, combs, hats that come into contact with hair
- Wash hair three times a week, apply conditioner and wet comb with a fine-toothed comb to ensure infestation is really gone, and to help prevent reinfection.
And if tackling head lice has left you feeling stressed, have a laugh and unwind with the following clips. For the pediculocide mentioned, use a neem oil product….
Instead of the olive oil used in Part 2, below, use one of the dimethicone products I’ve reviewed above (one of which you can leave overnight as with the olive oil). If you don’t mind the gloopy mess, olive oil is always another option, however, though I feel this is best left in the kitchen now that silicone-based remedies are available.
Hope you’ve found my review helpful – do let me know how you get on with tackling these little pests, and getting rid of headlice!
Image credits: gilles_san_martin/flicker; wellcome_library/wikimedia; community_hygiene_concenr/wikimedia