SAN ANTONIO -- New research warns head lice in Texas and around the country are becoming harder to kill.
A study from Southern Illinois University found lice in at least 25 states have developed resistance to ingredients found in common, over-the-counter remedies.
Dr. Sky Izaddoost, a pediatrician with the Children's Hospital of San Antonio Physician Group, says even if a portion of the lice in the area are resistant, that can have a big impact.
"It will kill some of them, but not all of them, and that's the big concern," said Dr. Izaddoost. "If one of them survives, they have the potential of making more."
Molly Keck, an entomologist with the Texas A&M AgriLife Extension, says drug resistance is fairly common.
As a treatment gets used over and over, genetic defenses get passed on.
"Whatever reason they're not dying, they pass that on to their offspring," said Keck. "You have a whole population of lice that's not affected by this treatment."
Keck estimates more than half the lice in Texas will barely bat an eye at most over-the-counter treatments.
Prescription medication will work, but Dr. Izaddoost says those can cost upwards of $100, much more expensive than their store-bought counterparts.
"The private insurers are kind of weary about covering something like that," said Dr. Izaddoost. "And worse, usually when you're that far along, you want to treat the whole family."
Dr. Izzaddoost she still recommends trying the over-the-counter treatments before prescribing in order to try and avoid paying too much.
She says parents should be prepared in case that doesn't work.