Mutated Head Lice Resistant To Common Repellent In 25 States

 Parents beware. Scalp-irritating lice have developed resistance to a common chemical in as many 25 states of the US, a new study warns.

Head lice infestations are common during childhood, forcing children to scratch the scalp out in severe cases. Lice are known to spread in a group whose members have close contact like sitting next to each other. Though they do not cause disease, lice infestation can be severe enough to force children to miss school.

Pyrethroids which include the ingredient permethrin is the first line of treatment available over-the-counter. Researchers found that in most states lice have mutated to become resistant to the chemical.

"What we found was that 104 out of the 109 lice populations we tested had high levels of gene mutations, which have been linked to resistance to pyrethroids," said researcher Kyong Yoon of Southern Illinois University.

Yoon and colleagues tested pests for a trio of resistance-rending genetic mutations, collectively known as kdr. They found lice samples from 25 states had all the mutations while samples in four states, New York, New Jersey, New Mexico and Oregon, had one, two or three mutations. Only lice in Michigan did not have even one mutation. Researchers are now investigating just why lice in the state have not developed resistance.