There is nothing more likely to strike terror through a mum's heart than the dreaded nit text from school.
Usually it appears some time mid afternoon, before pick up, just as I'm wondering whether I can get all the children in bed and asleep before the start of Midsummer Murders and a glass of white wine.
Then up it pings: 'There has been a case of head lice in your child's class. Please check their head and treat.'
With that one ominous sentence I am suddenly faced with an evening of unimaginable stress.
I have four children and even if they have been lucky enough to escape the blasted crawlies it is still going to take me at least an hour to check all their heads.
Two of them have long hair so there will be tangles, tears and tantrums. I will grimly brandish the nit comb, threatening a wide array of punishments if they don't Just Stand Still and my own head will itch, hours later in bed, even though I know it's a purely psychosomatic reaction.
That's the best-case scenario. The worst is something we mothers dread even more: once those lice claim tenants' rights in your child's hair, you're in hell.
Trust me, I have tried everything. And I am not one of those softy mothers who worry about insecticides on my little darlings' heads. In the case of nits my view has always been 'Bring on the toxic chemicals.' I remember once using a treatment so strong my daughter's eyes were streaming and she was begging me to wash it off because it stung her scalp so much. I pointed out to her that in the old days they would shave children's heads and then smother their scalps in Kerosene so what on earth was she making such a fuss about?
According to leading UK head lice expert Ian Burgess, director of the Medical Entomology Centre (which researches not only nits, but also cockroaches, fleas and bed bugs), between eight and 15 per cent of children in the UK are affected by head lice at any one time. It's a national endemic and it seems none of us – adults included – are immune.
Even David Cameron was, last week, forced to admit at a Downing Street event that they had some unwanted visitors in No. 10. The Prime Minister revealed that his children had come home from school with nits and he offered to supply journalists with shampoo and a comb to check their heads later.
But as he will probably have discovered, admitting to head lice is one thing. Banishing them from the house is quite another – one which leaves the task of reducing national debt seem quite easy in comparison.
The problem, according to experts, is that lice have become wholly resistant to treatments containing insecticides and parents have got out of the habit of making regular checks of their children's hair.
"Lice have such a quick reproductive cycle infestations occur very rapidly," says Ian Burgess. "The female louse only needs to mate once and she can lay six eggs a day – 150 over her lifetime – which is, on average, 30 days"
It's an alarming thought, even more so when you see an army of these blood-sucking critters clinging for dear life to your child's scalp. But this pales in comparison to the trauma of trying to get rid of them.
Once, they hijacked the heads of my entire family (although I think they may have asked for their money back when they landed on my husband, Keith, who is going a bit bald). Once I'd treated and combed all the dead lice from the children's hair I then had to do Keith's, which didn't take long, and he had to do mine.
It was late – the 10 o'clock news had long since finished - and after about five minutes of cursory combing through my locks he yawned and said: 'I'm bored. Can I go to sleep now?'
That's men for you. Unfortunately, getting rid of your own lice is a bit like blow drying – almost impossible to do well alone. And sure enough, three weeks later, we were repeating the de-nitting nightmare all over again.
On another occasion it was national 'Bring your daughter to work day.' Flo was only seven and terribly excited to see 'Mummy's office' and all her colleagues. So too, were the lice living on her head. They were practically jumping up and down with enthusiasm. The following day I watched, in horror, as my editor called a brainstorming meeting and proceeded to scratch her scalp the entire way through. But that's the thing about nits. They're really not too picky where they land.
• Lice can't be caught from hats, they don't always make people itch, and it's not just children that have them.
• Lice can't jump or fly but are passed on by close contact.
• They don't prefer shiny clean hair. And if you've short hair you're not immune.
• Head lice are brown, six-legged insects that stick tightly to the hair shaft and take about seven days to hatch.
• Unhatched or empty eggs are known as nits. Treatment is needed only if you see one or more live lice. Nits do not always mean that you are infested with lice. They can stick to hair even when lice are gone
• Lice walk from one head to another. That's why small children are most affected as they play and work very closely together.
• A full-grown louse can crawl 9in in a minute and is genetically programmed to move on to new heads.
• There is no need to treat bedding and clothing. Lice only move if they think they can reach another head. If they are found on clothing or bedding they are already dying.
• Lice have nit-nav. If one falls it will keep climbing until it reaches a head or can get no higher.
• It is much easier to rid the scalp of lice, which measure about 3mm long when fully grown, than during the early stages of infestation.
Ian Burgess recommends using products which contain a physical agent such as silicone - which smother the lice – and are now regarded as more effective than traditional insecticides. Lice do not urinate so they get rid of excess fluid via their windpipe. The silicone blocks their airways and they die or explode.
Hedrin Once: A clinical study published last week revealed this is currently the most effective product on the market for killing lice. Recent trials proved it was 100 per cent effective after just one, fifteen-minute application.
Derbac M and Quellada M: Both insecticides. A 2002 trial reported a 75 per cent success rate, but a study published in the British Medical Association three years later found one application cleared only 17 per cent of cases. Ian Burgess says this is because lots of lice have built up a resistance.
Lyclear: Also an insecticide containing permethrin. A 2002 trial found it eradicated 33 per cent of cases in one application and 78 per cent were free of lice after a second application. But a study two years later showed only 55 per cent success with two applications. Can cause a rash.
Wet combing: Also known as bug busting, this involves coating the hair with conditioner to immobilise lice then using a fine toothcomb to remove them. It is the cheapest option as you can reuse the comb, but requires patience and time and a 2005 study found it worked in only 57 per cent of cases. Hair must be sectioned and combed systematically, from the roots to the ends and you will need to repeat the process every three days for two weeks.
Dry combing: More difficult, particularly with curly hair. Easier to identify lice, particularly if you do it over a white sink. There is a danger lice will be flung around by static electricity, causing them to spread.
Electric combs: Burgess says they will kill larger lice but may miss nymphs that have just hatched.
Some swear by the effectiveness of tea tree oil and a team of scientists in Australia, led by the nation's head lice expert, Professor Richard Speare conducted studies which concluded tea tree oil was the only treatment to achieve a 90 per cent kill rate over a three hour period. But Burgess believes lice have built a resistance to this too.
Two or three drops of tea tree oil can be mixed with any brand of shampoo or olive oil and then rubbed or combed through the hair.
Leave on the hair for a minute before rinsing thoroughly. Repeat daily for a week or until lice and any remaining eggs (nits) have gone.
For more information and a bug busting kit visit www.chc.org