Just thinking about head lice is enough to make you squirm, but it’s a problem most parents have to contend with a some point.
At any given time, two million under 16 year olds in the UK are suffering from an infestation, NYDA statistics show.
And in the US, up to 12 million children aged three-to-11 are thought to be struck down every year, according to the Centers for Disease Control and Prevention.
Although commonplace, a host of myths - like lice being able to fly - make the bugs harder to avoid and eradicate.
With a number of UK schools back for a new half term next week and today marking National Bug Busting Day, Yahoo UK asks an expert how to dodge, and treat, an infestation.
What are head lice? And how do they spread?
Head lice are small insects that measure up to 3mm (0.11 inch) in length, according to the NHS.
Their eggs, or “nits”, are brown and turn white after hatching.
Head lice can cause incessant itching and a feeling of something moving in your hair.
Contrary to common belief, head lice cannot fly or jump.
The insects typically pass from person-to-person by walking along strands of hair while the heads are touching.
“This is why children tend to pick them up easily as they spend a lot of their day playing with other children, often with their heads together,” Dr Sarah Brewer, GP and medical director of Healthspan, told Yahoo UK.
While it may seem an inefficient way to get about, lice move fast.
The adult critters get about at a pace of around 23cm (9 inches) a minute.
A study by the Medical College of Ohio even found they can “drop” onto shoulders.
The discovery came about after an outbreak in a US school left 17 teachers with an infestation, despite them insisting their head had not touched anyone else’s.
“The scientists found when a head louse senses danger such as bright light, an unpleasant odour (including lice repellents) or hair agitation (brushing), 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,” Dr Brewer said.
“This hopping off reaction is an effective mode of transmission.”
Lice are also hardy. Adults can survive for up to three days without feeding on blood and their nits can hatch 10 days after being separated from a “host”, according to Dr Brewer.
Whether lurking on a towel, bedding, clothes, carpet or hairbrush, the insects have plenty of time to find a new host.
A study by James Cook University in Australia found that out of 48 people with head lice, two had live insects on their pillowcases.
How to get rid of head lice
When it comes to removing head lice, physically brushing them out - however laborious - may be most effective.
“Over the last 20 years, head lice have built up considerable resistance to chemical insecticides,” Dr Brewer said.
“As the larvae have multiple outer shells they often survive by shedding their outermost casing to receive a sublethal dose.
“Of those used, malathion has retained the most effectiveness (78%). However, malathion acts as a nerve toxin and its use should be limited in children.”
Wetting hair before removing lice and nits with a fine-toothed comb may be the best way to combat an infestation.
“After shampooing and conditioning the hair, place a white towel around the child’s shoulders, and comb out any tangles with an ordinary comb,” Dr Brewer said. “Then apply a little more conditioner.
“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 (e.g. while watching TV) and repeat every three-to-four days, for two weeks, to remove newly hatched lice and nits.
“It is effective in almost 60% of cases but you only have to miss one fertilised adult female for the infestation to start up again.
“I found the most effective way was to get my kids to kneel with their wet hair over the bath, so I could comb away from myself and dislodge the 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.”
Most importantly, lice should never be left in the hope they will just “go away on their own”.
“A mature female lays five-to-10 eggs each night,” Dr Brewer said.
“An adult female lays up to 300 eggs before dying around 30 days after reaching adulthood.
“An average host carries around 20 adult female lice which, during their 30-day life cycle, have been shown to lay 2,652 eggs.
“If left untreated, as many as 5,000 lice may hatch within three months. It is the sheer number of eggs produced that can make an infestation so difficult to eradicate.”
If after 17 days of brushing the infestation has not let up, the NHS recommends you go to a pharmacist for advice. They may suggest medicated lotions or sprays.
While it may be tempting to keep your child off school while battling head lice, the health service stresses there is “no need”.
Itching comes about due to an over-reaction to the saliva head lice release while feeding.
This usually does not start until four-to-six weeks into the infestation, Dr Brewer said.
Your infested child may therefore have been attending school, spreading their head lice, for more than a month before the insects are spotted.
You also shouldn’t beat yourself up for the infestation. Research has found no link between cleanliness and the risk of head lice.
If an infestation does spring up in your household, everyone should be vigilant.
“Brisk brushing, twice a day, with an old-fashioned bristly brush (plastic and spiky ones don’t work) can help,” Dr Brewer said.
“This knocks the legs off lice so they cannot hold on, or feed.”
To prevent the infestation returning after all your hard work, Dr Brewer recommends washing pillows in a tumble dryer for 15 minutes or blasting them with a hair dryer to kill any lingering critters.
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