Newfound resistance to treatment products puts tactics back in focus
By Dennis Thompson
HealthDay Reporter
(HealthDay News) -- Head lice are perfectly adapted human predators, capable of surviving the worst we dish out and continuing to come back for more.
And they are getting even tougher.
Researchers have found that head lice are becoming resistant to the products people rub into their children's hair to kill off the pests.
"The lice appear to have developed the ability not to be killed by these products," said W. Steven Pray, a pharmacy professor at Southwestern Oklahoma State University. "It's just driving people nuts out there."
Medical experts appear to be veering into two camps in facing this issue. Some are looking for more effective lice-killing treatments, and others are urging a return to simpler treatments that involved combing and picking nits from the scalp.
With September designated as Head Lice Prevention Month, health-care experts want to help educate parents about the parasites as their children re-enter the close confines of school classrooms.
Head lice tend to lurk in people's scalp, eyebrows and eyelashes, according to the U.S. Centers for Disease Control and Prevention. They feed on human blood several times a day but are not known to spread disease.
"They are perfectly evolved for what they do," Pray said. "They blend into our background skin. They are elegantly designed for the job they have, which is to live on our blood."
The CDC estimates that 6 to 12 million head lice infestations occur each year in the United States among children 3 to 11 years old.
Head lice can't hop or fly so they have to move by crawling. Generally they spread during close human contact or when someone comes in contact with clothing or other items that have touched the head of an infested person, according to the CDC. Personal hygiene and cleanliness are not factors in the spread of head lice. (If your child gets head lice, it's not because you keep a dirty home.)
"Little kids get it more often than older kids and adults because their personal space is smaller," said Dr. Barbara Frankowski, a pediatrician in Burlington, Vt. "They hug each other. They play with each other on the floor."
Head lice are visible to the naked eye, although they are tiny. An adult louse is about the size of a sesame seed. Its eggs look like tiny tan, yellow or brown dots. Other signs and symptoms of a head lice infestation include:
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A tickling feeling along your scalp, or the sensation of something moving in your hair.
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Itching caused by an allergic reaction to lice bites.
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Difficulty sleeping. (Head lice become most active in the dark.)
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Head sores caused by scratching.
Various over-the-counter and prescription treatments are available to help kill lice. These insecticides usually come in the form of a medicated shampoo, lotion or cream rinse.
Researchers have found evidence, though, that head lice are becoming more resistant to the treatments. The resistance is suspected to come from several factors:
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Head lice are simply good at adapting. "That's one of the things bugs do best, is develop resistance," Frankowski said.
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Parents misapply the medication, exposing the lice to the insecticide without killing them.
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Parents treat to kill the lice but forget to re-treat to kill the lice that later hatch from eggs unaffected by the insecticide.
Frankowski said that new products coming onto the market should be more effective against lice. One product, for instance, works by drying out the pests. "It holds their little breathing sphericals open, and they dehydrate," she said.
Pray believes the best way to take care of lice is to weed them out with a fine-toothed comb. That's a time-consuming process, but it rids the child of lice and eggs without exposure to the insecticides in the medications that are available. It also makes resistance a moot point.
Frankowski favors a combination approach. "The live lice will run away from where you're combing," she said. "I recommend using a product that gets the live lice first. Kill them, and then comb for 15 to 30 minutes every evening for the next 10 days and you should get out all the nits and eggs that are hatching."
The CDC also recommends that people who don't have success with one product should try another because head lice in certain regions will be resistant to one type of insecticide but not the other.
"We need the [Food and Drug Administration] to look into this far more than they ever have before," Pray said. "Really tackle the issue of resistance and why we are getting so many reports from patients that the lice just aren't succumbing to over-the-counter products."
On the Web
The Nemours Foundation has more information on head lice.
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