Head lice: The idea alone is enough to make your scalp itch.
Each year, there are 6 million to 12 million lice cases in U.S. children ages 3 to 11, according to the Centers for Disease Control and Prevention. It's a year-round scourge, though the number of cases seems to peak when kids go back to school in the fall and again in January, possibly due to familial mingling during the holidays.
There are almost as many misconceptions about the parasites as there are critters. M.J. Eckert, a former school nurse and co-founder of Lice Happens, an Annapolis, Md.-based in-home lice treatment and removal service, says she once met a father who'd used a high-powered shop vacuum on his son's infested head, hoping to suck the problem away.
Another family threw out a sleeper sofa in the middle of the night, convinced that it was the source of an intractable lice infestation. Neither approach worked.
First, some facts: The head louse is a six-legged, wingless insect known as an ectoparasite, meaning that it makes its home on a host's surface. It's related to the body louse, which, unlike the head louse, can carry disease.
The animal needs blood and a warm environment to survive. That's why it finds such comfort in the human scalp; it also likes to root itself in the nape of the neck and behind the ears.
Once it has set up shop, the insect lays pinhead-size tan or whitish-colored eggs, known as nits. The mother louse excretes a kind of glue to cement the nits to the hair shaft, close to the scalp so its warmth can incubate them.
They hatch about a week later into baby lice, called nymphs. In a typical infestation, there are more nits than bugs since an adult louse will lay an average of five to 10 eggs a day and a newborn female needs only 10 days to become a mom. So the family tree grows quickly.
Head lice are undeniably gross. Eckert says she faces tears and panic from parents every day. "Seeing (lice) in their kid's hair," Eckert says, "makes a normally sane person insane."
The American Association of Pediatrics suggests that kids with lice stay in school: "Because a child with an active head lice infestation likely has had the infestation for one month or more by the time it is discovered and poses little risk to others from the infestation," its guidelines say.
"He or she should remain in class but be discouraged from close direct head contact with others."
It doesn't help that there's such confusion about how the little beasts operate. Here are a few common myths:
You're more likely to get lice if you're dirty: "Head lice has nothing to do with hygiene," says Andrew Bonwit, a pediatric infectious-disease expert at Loyola University Health System outside Chicago. "It has to do with whether the person was exposed to someone with head lice."
Bonwit says a louse, which is "about the length of George Washington's nose on a quarter," doesn't have discriminating tastes. It wants warmth for its eggs and a regular "blood meal." It doesn't matter if the dish is dirty or clean.
Your pet can carry lice: Lice feed only on humans. Fleas and ticks are another story.
Lice can jump and fly: No. They just crawl. That's why kids are so much more likely than adults to have lice: They often touch heads when interacting, whether playing or talking or sleeping together at slumber parties (which are top-notch settings for lice transmission).