Teenager John was doing his homework when a bug fell onto his school book.
"For about 10 minutes I didn't process what it was, and just started playing with it," says the 15-year-old from Maryland in the US.
"Then I finally realised - this fell out of my head. This is in an insect, this is a head louse."
The discovery prompted a ritual familiar to millions of parents around the world - John's mother and father bought an over-the-counter chemical treatment, and "bug bombed" his head.
"But it didn't work," says John's mum Jerri.
While exact statistics are hard to come by, getting head lice is a rite of passage for most schoolchildren.
In the US alone, as many as 12 million kids per year get an infestation, according to the federal public health body, the Centers for Disease Control and Prevention.
Meanwhile, a 2011 survey found that one third of under-16s in the UK had caught head lice in the previous 12 months.
24-hour 'lice line'
The problem for families trying to get rid of head lice is that over the past few decades the insects have built up a resistance to many of the available pesticide treatments.
So simply spraying or shampooing your child's hair with one of these products can often not work against these toughened "super lice".
Thankfully for stressed-out mums and dads - and itchy children - in recent years a new industry has built up on both sides of the Atlantic as a response: professional head lice removal companies.
One such business is Lice Happens, based in Annapolis, Maryland, an hour's drive east of US capital Washington DC.
The firm, who came to the rescue of John and his mum, runs a 24-hour emergency "lice line".
Once a time has been arranged, Lice Happens will visit a family's home.
Wearing special headsets fitted with magnifying glasses, staff are armed with professional grade "nit combs", and use a pesticide-free and non-toxic spray to loosen and comb out both lice and their eggs (nits).
Fact from fiction
An average session costs from $300 (£244), and all family members are screened.
"It only takes one appointment," says Lice Happens' owner Nancy Fields, who set up the business in 2008.
"And while we work we educate, because there is so much misinformation out there. We make sure people understand fact from fiction, and give them hands-on training.
"We show parents how to accurately screen their children, and if they find they have to deal with lice again, we remind them of their training, and guide them so they don't have to throw more money at it.
"Instead of looking at it as an expense, it's a one-time investment."
Head lice facts
- They cannot jump or fly; instead they spread by head-to-head contact
- The average infestation totals about 20 lice
- A female louse typically lives for a month, laying five to 10 eggs or nits per day
- They feed by sucking blood from the scalp
- Eggs take seven to 11 days to hatch
- In the UK hairdressers are legally required to refuse custom to someone with head lice
Ms Fields decided to set up Lice Happens after helping her sister battle an infestation. "My sister was doing everything she could, but it didn't work," she says.
"She was also having to take unpaid leave from a new job to look after her children because the school wouldn't admit them while they were infected.
"It got me thinking that there has to be a better process, and that inspired me to think about starting a service to help people like my sister."
'Not just nit picking'
Ms Fields and her business partner MJ Eckert have since grown the business by selling area franchises for $29,000.
There are now eight franchises across the US, and about 50 people employed in the business.
Ms Fields says: "We're picky about who we're going to award a franchise to.
"It's not just about nit picking anymore, it's about supporting people who have invested a considerable amount of money, and that's a lot of responsibility."
Ms Fields adds that she and Ms Eckert now make six-figure annual salaries.
"It's not like we've won the lottery, but we're able to pay our bills," she says.
Stressed parents, bullied kids
In the UK, another head lice removal business expanding via the franchise model is The Hairforce, which was set up in 2006 by Dee Wright.
She says she was inspired to set up the company after reading an article about a US lice removal business.
The Hairforce takes a hi-tech approach, and its "crack squad of lice assassins" get rid of lice using a three-stage process. First they use a handheld vacuum system to gently suck out any living lice.
Then they use heated air to dehydrate and destroy all the eggs, and finally they apply a natural hair conditioner and use nit combs to remove everything.
"The conditioner is just to remove any static energy, and lubricate the hairs to prevent any from tearing," says Ms Wright.
The first appointment lasts for 90 minutes, and costs £100. A week later the three stages are repeated in a second appointment that costs £50.
After establishing the business in north London, it has now spread across the UK. Employing 30 people, Ms Wright says the company treats "thousands" of people every week.
"We really do fulfil a real need," she says. "We see mums and dads who have spent a fortune on expensive lotions that just haven't worked, and they come to us very upset and stressed, their children bullied at school.
"What we see is children transformed from the first to the second appointment. Parents often say they have got their child back."