But experts say parents shouldn't let panic upend their home needlessly as they race about trying to rid their kids - and possibly themselves - of the sesame seed-sized parasites.
People tend to just freak with this, says Steve Pray, a professor at the School of Pharmacy at Southwestern Oklahoma State University in the US. One of the first things you have to do in a counselling session is calm them down. A minimalist approach is going to be better here.
Millions around the globe affected
Another thing you should realise about head lice is you're not alone.
As many as six million to 12 million people worldwide get head lice every year, according to the US Centers for Disease Control and Prevention. And cleanliness has nothing to do with who will be the targets of the blood-sucking insects.
Read: What are head lice?
Preschool and elementary-age children, aged three to 10, and their families are infested most often. Children tend to pass lice along at school when they share hats or play closely with other kids.
White people get head lice more often than other racial groups. And girls and women tend to get them more often than boys or men because their hair is longer, says Dr Mervyn Elgart, emeritus professor of dermatology at George Washington University.
Having short hair is a blessing, Elgart says. Lice like to be warm, and if you've got longer hair it's warmer under there.
How to get rid of lice
So how do you rid your child or yourself of these pests?
The first decision is whether to use a chemical shampoo.
Some experts warn against it, saying the shampoos contain harmful ingredients. It's a pesticide, and there are safer alternatives, says Deborah Altschuler, president of the American National Pediculosis Association. It makes no sense to shampoo a child with a pesticide.
Read: Preventing head lice
Altschuler and Pray also warn that the lice shampoos currently on the market are becoming less effective. We have a great deal of resistance that's emerging, the same sort of resistance we're seeing in antibiotics, Pray says. I'm having people come in and say they've used the products perfectly and they just aren't working.
Choose the right product
But Elgart believes some shampoo treatments can be safe and effective. We use chemicals to colour hair. We use chemicals to curl or straighten hair. I think the appropriate use of chemicals isn't so bad, he says.
Elgart recommends products that contain the pesticide permethrin. Over-the-counter treatments contain one percent permethrin, but Elgart says people with more stubborn cases can get a five percent permethrin solution with a prescription.
Altschuler and Pray suggest people remove the lice and their eggs (called nits) using special, fine-toothed lice-removal combs, which pull the insects from the scalp.
Read: Treating head lice
Both say people should definitely stay clear of chemical treatments if the affected children are on medication or are receiving therapies for Aids, cancer, epilepsy, asthma, allergies or any other chronic illness.
Combing the hair
Once parents have combed their children's hair for lice and nits, they should comb their own hair in the shower, Altschuler says, but not before boiling or washing the comb between uses.
One problem with combing is that the nits stick to the hair follicle using a very strong glue. Elgart recommends soaking the comb in vinegar before using it to help dissolve the glue.
Home remedies can be dangerous
Pray warns people against home remedies. He's heard of people using gasoline or kerosene on their children, or pesticides straight from their garden store. Other home remedies he's heard of involve coating the head in Vaseline, olive oil or salt water.
They're embarrassed, so they won't come to pharmacists and get the straight information, he says. It's just incredible what people do.
The embarrassing thing is not that you've got it. It's not treating it and having your child go to school and infest others, Pray adds.
Lice need human blood
If lice strike your family, don't worry about having your pets treated. Nor should you coat your house with pesticides. Head lice feed specifically on human blood, not animal blood, and don't stray far from their food source.
They're not going to strike out on expeditions to find new heads, Pray says. Away from a person they're going to die within 24 hours, because they must have human blood.
But you should vacuum your home thoroughly and wash your clothes and linens in hot water. These things (lice) are very temperature-sensitive, Pray says.