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Managing head lice

The topic of head lice is never far from the minds of parents and carers. Pharmacy teams can be on hand with advice.

As a new school year gets underway, the topic of head lice won’t be far from the minds of parents and carers. Pharmacy teams can be on hand with advice and recommendations

Following lockdowns, disrupted schooling and summer holidays, parents may be out of the habit of checking their children’s heads regularly for head lice, but keeping on top of these tiny parasites is key.

In March 2021, international recommendations for the effective control of head lice infections, published in the International Journal of Dermatology, stressed the importance of regular detection combing, and treatment where necessary, to prevent the spread of head lice infections.

“Head lice have been living with humans for over 10,000 years and remain prevalent, although recent lockdowns and social distancing have shown a slight reduction,” says Dr Tess McPherson, spokesperson for the British Association of Dermatologists. “Unfortunately, lice are practically a certainty for children and young people at some stage of their life.”

All about head lice

Head lice (Pediculus capitis) are tiny grey-brown insects that live on human scalps, feeding on human blood. They affect mainly children between the ages of four and 13 years, with girls diagnosed more often than boys. Head lice can affect people with any hair length, no matter how clean their hair is, and can spread easily throughout households, especially in those with several children.

Head lice have to feed on human blood several times a day to survive, and will die if they leave the human scalp for a day or two. They can’t jump or fly, but they can walk from head to head – it takes about 30 seconds for a single louse to move from one scalp to another. Louse eggs are laid close to the scalp and hatch after seven to 10 days. The term ‘nits’ refers to the empty eggshells and not the lice themselves. Baby lice become fully grown, and the females are able to lay eggs, after around seven days.

Detection methods

Many people with head lice don’t realise they have an infection, as only some people will get an itchy scalp. If the infection is left untreated for a long time, it can lead to complications. Intense itching may lead to sleeping problems and a loss of concentration at work or school, and repeated scratching may increase the risk of bacterial skin infections. Some children may have a rash behind their ears or on the back of their neck. Head lice can also cause emotional and psychological problems, due to social stigma and fear of exposure. This is because of the misconception among some parents and children that the infection is related to poor hygiene.

Head lice should only be diagnosed if a living louse is found on the scalp. An itchy scalp or the presence of nits doesn’t mean there’s an active infection. While head lice may sometimes be found by simply looking at the hair, they are tiny (around the size of a sesame seed) and difficult to spot. In most cases, the only way to know if a child has head lice is to inspect the scalp using a fine-toothed detection comb.

According to the March 2021 international recommendations, a louse comb with teeth spaced 0.20-0.30mm apart is particularly effective at ‘filtering’ lice and their eggs from the hair. Parents should check for head lice whenever they wash their children’s hair, or once or twice a week. Wet combing – wetting the hair, then applying conditioner before combing – is more effective, and usually less painful, than dry combing.

Ian Burgess, director of the Medical Entomology Centre in Cambridge, says it’s important that pharmacies are stocking the right combs. “Many of the head lice combs sold for detection are not fit for purpose,” he says. “The teeth may be too wide or too flexible. The metal teeth may actually be too rigid and sometimes too close together, while other combs are either too wide or have a long taper at the tip that lets lice slip through. Teeth should be square-faced plastic and not more than 0.30mm apart.”

If head lice are found on one person, all other members of the household should be examined. All affected household members should be treated at the same time on the same day if possible, but people don’t need to be treated if no living head lice are found on their scalp.

Treatment options

Head lice should be treated as soon as possible using a wet combing method first. If this has been tried for 17 days without success, a physical insecticide such as dimeticone or cyclomethicone can be tried. Herbal and essential oil preparations aren’t recommended as there is insufficient research to support their use. There is no need to treat clothing or bedding as head lice can’t live on these for long.

Wet combing

Wet combing is recommended by the NHS as the first-line treatment. Using the correct comb and following the instructions carefully is important, according to the international recommendations. This involves systematically combing hair that’s saturated in conditioner, using a fine-toothed comb.

According to Joanna Ibarra at the charity Community Hygiene Concern, wet combing with conditioner suits all incomes. “It’s not very expensive, is proven to work in clinical trials and families can use the combs again and again,” she says. “It’s also better for the environment than using formulated head lice products. Using so much conditioner on the hair makes it soft and silky, and then families can use [a head lice] comb, with teeth much closer together, to sweep off nits afterwards – these are the cause of stigmatisation among children at school.”

Joanna says that head lice stay still when they are wet, usually at the roots of the hairs, which makes them easier to remove. “Using conditioner will keep them wet for even longer,” she says. “Use a wide-toothed comb first to make it easier to comb out any tangles. Then use [a head lice] comb to comb lice off the hair. Do this four times in succession, spaced out over two weeks, to remove all hatched lice. Lice don’t leave the head until they are fully grown, and lice can’t reproduce until they are fully grown, so combing can prevent the spread.”

Separate plastic combs should be used for the detection and removal of lice and nit removal. Parents should check the fine-toothed comb carefully after every stroke and then wipe it clean. It can take up to 30 minutes to properly comb a head of hair.

Detailed information on wet combing is available on the Community Hygiene Concern website at:

Physical treatments

Using physical treatments is the next step to try if head lice persist after wet combing for 17 days. “Parents should always follow the instructions on the package as exactly written,” she advises. “Some treatments contain harsh chemicals and should be treated with caution. Children should never apply the product themselves. It’s also important to ensure the product is rinsed off properly, and other patches of the child’s skin should be avoided as much as possible.”

Physical insecticides, such as dimeticone, coat head lice and kill them through suffocation. These products should be applied to dry hair, to all areas of the scalp and to all hairs from their roots to their tips. They need to be left on for the recommended length of time. The treatment should be applied on day one and a week later (day eight) to kill off newly hatched lice. Parents should use a fine-toothed comb to remove lice from the hair and scalp.

“Apply the product thoroughly, preferably spreading the fluid with a comb (not using a nit comb, but it could be a detection comb),” says Ian. “Leave it on for at least as long as the instructions state. Wash off thoroughly with shampoo, applying the shampoo before the water. Check for lice survivors and, more importantly, hatching juvenile lice over the next week or so. Repeat as necessary.”

Chemical treatments

Chemical insecticides poison head lice by stopping their nervous system from working properly. In the UK, the only recommended chemical insecticide is malathion 0.5% aqueous liquid, but this should not be used as a first-line treatment. “These [products] are seriously impacted by insecticide resistance,” explains Ian. “In some areas, this message doesn’t seem to have got through to some clinical practitioners. The problem is they are still on the Drug Tariff, so they get prescribed for the people most in need of support and least able to manage the problem for other reasons.”

Treatment failure

After completing the treatments, parents should continue to check for head lice every week, to ensure that the infection has cleared up.

If head lice are still present, they may not have followed the instructions correctly or repeated the treatment at the correct intervals. It is also possible that the child may have picked up another infection immediately after the treatment finished – their close contacts and household members should be rechecked for head lice.

“A common mistake with wet combing is to not read the instructions carefully to prepare the hair properly before using the fine-toothed comb,” says Joanna. “Pharmacies should have a kit open and go through the instructions step by step with the customer before they buy one.”

There are also concerns among some experts that head lice may be coming resistant to some physical treatments. Ian says that there is currently no proof of this, but “some products are not working as well as they used to”, he says.

Preventing head lice

Children with head lice do not need to stay off school because the infection is likely to have been present for several days or even weeks before it’s discovered. But all parents should be asked to check their children’s hair and treat if head lice are found.

Head lice infections cannot be prevented, although tying back long hair at school and during social gatherings can help to an extent. “Behaviour changes don’t last long, especially with small children. Try telling a seven-year-old not to have close contact with their friends,” says Ian. “There is no evidence that repellents work, and even protective products that slowly kill lice when they come in contact have limited effect – just because something is statistically significant does not mean it is effective. The concentrations of essential oils [in most of these preparations] is too low; since there is a crossover in metabolism between several possibly active components of essential oils and conventional insecticides, we should consider the lice resistant to them.”

Other parasitic infections

Head lice aren’t the only parasitic infection that children – and adults – are vulnerable to.


Threadworms – also known as pinworms – are tiny worms that look like little pieces of white thread. They are common in young children and spread easily when their eggs are swallowed. The worms can cause intense itching of the anus and/or vagina, and may be seen at night around the anus. Occasionally, they can cause weight loss, bedwetting and skin irritation.

Threadworms are easily treated with mebendazole, which is available over the counter as a chewable tablet or liquid. Everyone in the household should be treated, even if they don’t have any symptoms. Not all products are suitable for children under two or pregnant or breastfeeding women – these customers may need to be referred to their GP.

Threadworm eggs can live for up to two weeks outside the body on surfaces. Scrupulous hygiene is essential, including washing hands and scrubbing under fingernails, especially before eating, after using the toilet and changing nappies. Parents should wash sleepwear, sheets, towels and soft toys at a high temperature, disinfect kitchen and bathroom surfaces and vacuum and dust all surfaces regularly.


Scabies are tiny mites that are spread by close or prolonged skin-to-skin contact. Anyone can get them, and they spread easily in communal settings, such as nurseries and nursing homes. Scabies burrow under the skin to lay their eggs, leaving tiny scratch marks and spots on the surface. They can cause intense itching, especially at night. Scratching can lead to skin infections and can make existing skin conditions such as eczema worse.

Scabies isn’t serious, but it does need treatment. The infection can be treated with a topical insecticide used all over the body, with a second application a week later. Crusted scabies, which is a more severe form, can occur in people with weak immune systems – these cases may require an oral insecticide (ivermectin) as well.

Scabies is highly infectious, but it can take up to eight weeks for the rash to appear. Everyone in the home needs to be treated at the same time, even if they have no symptoms, as well as any sexual partners from the previous eight weeks. Scabies can live away from the human host for up to 36 hours, so clothing and bedding need to be washed at high temperatures.

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