When a fellow parent leans across their child and mouths the words "We've had visitors", my heart sinks.

For it is a euphemism, not for a pleasant visit from friends and family but for a visit from the scourge of schooldays – Pediculus capitis, or head lice to you and me.

There seems to be more of them than there were in my day – the days of the nit nurse who used to throw your head forward and roughly part your hair as she searched for the tiny insects that live by sucking blood from the scalp.

In those days, if you were found with the creatures, you were taken out of the classroom and sent home with strict instructions not to return until they were gone. Nowadays, it seems, there seem to be some parents who treat them and others who don't, so once a class has them, it feels as if they stay there forever. No sooner have you got rid of them – than they're back. It is a never-ending circle.

It is more common in girls as they like to have their hair down, draping it over desks and, as they whisper to their friends, their hair gets entangled and the lice spread.

It doesn't seem to matter if you send them to school with their hair tied back, there's always a reason why the hair band had to come out.

The trick is to try and get the nits before they are turned to lice.

The nits are the eggs that are laid to the base of hair – commonly found behind the ears and at the nape of the neck where children sweat.

And we've tried every lotion on the chemist's shelves as well as old wives' remedies we've picked up along the way. Much to my daughter's indignation, I once tried soaking her hair in vinegar – the result was a child that was smelling like a fish and chip shop, and me getting very stressed trying to get rid of the smell in time for her to go to school.

Even the slightest sign of head scratching is enough to send me hunting for the nit comb – a metal one that I'm sure our descendants will look upon as some sort of instrument of torture. In fact, my daughters probably think it is now!

Even writing about it is making me itch.

They say head lice only settle on clean hair – that is a myth as lice don't have any preference. And while it isn't a condition to be ashamed of, it is one that needs tackling.

Nits and head lice seem to be as much a part of school life as maths and English these days, but the best thing is prevention and in fact the message "we've had visitors" is one of the kindest, because others can then take action before there is another infestation.