If you see a bunch of lively school kids scratching their heads, chances are the dreaded head lice have moved in.
Reporter Brooke Hanson finds out the facts about why we get head lice and how to get rid of them.
Adults can catch head lice, but they're far more common in kids one in four primary schoolers will have them at any one time.
Brooke visits Sacred Heart Primary School in the Sydney suburb of Westmead to go to "nit-busting" class.
Head lice are parasites that are a little bigger than fleas and their eggs are what we call nits.
Glenis Lloyd is from the New South Wales "Nit-buster" program.
"What annoys parents the most is having spent all weekend getting head lice out of their kids' heads, for them to come home on Tuesday or Wednesday and they've got them again," she says.
Funnily enough, girls get head lice more often than boys. Not because their hair's lusher and longer but because of attendance at events like sleepovers.
"I call them head lice parties because what you're doing is moving head lice from one family to another family and back again," says Glenis.
At Marae Ishac's sleepover, her girlfriend's hair is about to brush against hers. At that very moment, a head louse turns into Tarzan.
"The head lice grips one hair shaft and literally swings to the next hair of the other person," says Glenis. "They don't jump or fly but they can swing quite fast."
Sure enough, a few days after her sleepover, Marae's got the dreaded head lice itch.
Brooke takes some of Marae's lice to Sydney's Westmead hospital to get a closer look at the tiny little nasties.
Dr Cameron Webb is a head lice expert. "This is adult head lice," he says, looking at the lice under a microscope. "You can see they've got six legs. There are no wings there. You can sort of see the head."
"The legs are really strong and thick," says Dr Webb. "And they've got claws on their legs, which make them perfect for holding on to human hair."
Meanwhile, Marae's mum, Rhonda has freaked out and flung herself into the usual damage control frenzy; stripping beds, and vacuuming floors and anywhere she suspects the dreaded lice might be lurking.
Is she doing the right thing? Can head lice live in pillowcases and bed sheets?
"That's another misconception actually, because the head lice can't live on doonas and pillowcases and things like that," says Dr Webb. "You're much better trying to spend the time removing the lice from the children's hair rather than overdoing the laundry and cleaning the house."
In fact, lice can't last a day off a human head.
So what's the best way to get rid of head lice, once they have moved into your child's hair?
There are stacks of head lice treatments to choose from, but Glenis says that the best treatment of all is wait for it ordinary old hair conditioner.
"You put lots of conditioner on," says Glenis. "Just get a cheap one and put a lot of conditioner through the kid's hair."
Apparently, the slimy conditioner clogs up the lice's breathing apparatus and stuns them for about twenty minutes.
"What we're looking for is not so much the eggs but the live critters themselves; the adults, the louse," says Glenis. "You'll see them when you start to comb through the hair."
Coated with conditioner, the poor old lice are too dopey to swing like Tarzan from hair to hair and you can catch them with a fine-toothed comb. Very fine combs with long, rounded stainless steel teeth work best. Comb every part of the head four or five times.
"You just wipe the comb on some kitchen paper and if they've got eggs or lice, you'll see them," finishes Glenis.
How simple is that? Better still, you can do this for every head lice attack because it's so chemically mild, the hair conditioner won't harm a single hair on the child's head.
"The comb and conditioner method is the one we prefer the most because there's no chemicals involved," says Dr Webb. "It's a bit time-consuming, but studies have shown that it's really successful"
So keep having sleepovers and forget washing all those sheets and pillowcases. Just keep a bottle of cheap hair conditioner and a fine-toothed lice comb in the bathroom. And most of all, remember that when your kids get head lice, it's no biggie!
Head lice only live in hair where there's a plentiful supply of blood, but you can't catch head lice from dogs or cats because lice only live on a diet of human blood.
Head lice don't carry disease.