--- title: Lice Are Now Resistant to Head Lice Treatment description: Lice in half of America—at least 25 states—are now resistant to over-the-counter treatments using permethrin and pyrethroids canonical: https://time.com/4000857/lice-treatment/ author: Mandy Oaklander article:opinion: false article:content_tier: free article:published_time: 2015-08-18T14:30:13.000Z article:modified_time: 2026-08-04T08:04:59.774Z article:section: Health og:title: Lice In At Least 25 States Is Now Resistant to Treatment og:description: Lice in half of America—at least 25 states—are now resistant to over-the-counter treatments using permethrin and pyrethroids og:url: https://time.com/4000857/lice-treatment/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltd8ec5e1b7b3a2ec1/6988604d428a9ee183ccebe6/rx-prescription-bottle-health-illo.jpg?branch=production&width=2400&quality=75&auto=webp&crop=16:9 og:image:width: 1200 og:image:height: 675 og:image:alt: TIME.com stock health rx prescription bottle drugs og:type: article twitter:card: summary_large_image twitter:title: Lice In At Least 25 States Is Now Resistant to Treatment twitter:description: Lice in half of America—at least 25 states—are now resistant to over-the-counter treatments using permethrin and pyrethroids twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltd8ec5e1b7b3a2ec1/6988604d428a9ee183ccebe6/rx-prescription-bottle-health-illo.jpg?branch=production&width=2400&quality=75&auto=webp&crop=16:9 ---  # Head Lice in 25 States Are Now Resistant to Treatment ## Video: Overstepping Boundaries: The Danger of Invasive Species [Watch (HLS stream): Overstepping Boundaries: The Danger of Invasive Species](https://cdn.jwplayer.com/manifests/zHyAT7e9.m3u8) (2:18)  _Published 2013-12-04. What are invasive species, and why are they dangerous? TIME's Bryan Walsh explains how animals like the Asian carp, lionfish, and Burmese python can be a threat._  by [Mandy Oaklander](https://time.com/author/mandy-oaklander/)  ## Mandy Oaklander Oaklander is a senior editor at TIME. Aug 18, 2015 2:30 PM UTC  Illustration by Sydney Rae Hass for TIME  by [Mandy Oaklander](https://time.com/author/mandy-oaklander/)  ## Mandy Oaklander Oaklander is a senior editor at TIME. Aug 18, 2015 2:30 PM UTC Here’s some lousy news: Lice in half of America—at least 25 states—are now resistant to over-the-counter treatments. That’s according to new research presented at the American Chemical Society’s national meeting. Study author Kyong S. Yoon, PhD, assistant professor in the Biological Sciences and Environmental Sciences Program at Southern Illinois University, has been researching lice since 2000\. (“My PhD entirely focused on head lice,” he says with a laugh.) Using the services of professional nitpickers across the country, Yoon decided to take an American lice census by collecting pest populations from every state. **MORE**: [Experts Claim Selfies Are Giving Teens Head Lice](http://time.com/9572/expert-claims-selfies-are-giving-teens-head-lice/) His research is still ongoing, but what he’s found so far in 109 samples from 30 states is startling: the vast majority of lice now carry genes that are super-resistant to the over-the-counter treatment used against them. Lice is commonly treated by a group of insecticides called pyrethroids, used for mosquito control. One of those, permethrin, is the active ingredient in some anti-lice treatments—but lice populations can develop a trio of mutations that make it resistant to pyrethroids. **MORE**: [Head Lice Is No Reason To Keep Kids Out Of School](http://content.time.com/time/health/article/0,8599,2006397,00.html) In 25 of the states, lice samples had all three of these genetic mutations, making them the most resistant to treatment. Lice populations from four other states had one, two or three mutations, and in just one state—Michigan—were the pests not resistant at all to the insecticide. “It’s a really, really serious problem right now in the U.S.,” Yoon says. Though head lice aren’t known to transmit any diseases, they can be an itchy nuisance—and now, they’re harder to kill. Yoon suggests prescription-based products, like ivermectin or spinosad, if pyrethroid-based treatments don’t work. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/4000857/lice-treatment/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/4000857/lice-treatment/"},"headline":"Head Lice in 25 States Are Now Resistant to Treatment","datePublished":"2015-08-18T14:30:13.000Z","dateModified":"2026-08-04T08:04:59.774Z","description":"A large number of lice populations have gene mutations that may make it resistant to over-the-counter treatments","url":"https://time.com/4000857/lice-treatment/","keywords":["Public Health"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltd8ec5e1b7b3a2ec1/6988604d428a9ee183ccebe6/rx-prescription-bottle-health-illo.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Mandy Oaklander","jobTitle":"Oaklander is a senior editor at TIME.","url":"https://time.com/author/mandy-oaklander/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltd8ec5e1b7b3a2ec1/6988604d428a9ee183ccebe6/rx-prescription-bottle-health-illo.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"TIME.com stock health rx prescription bottle drugs","caption":"TIME.com stock health rx prescription bottle drugs","creditText":"Illustration by Sydney Rae Hass for TIME","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/public-health/","name":"Public Health"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/4000857/lice-treatment/","name":"Head Lice in 25 States Are Now Resistant to Treatment"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"Overstepping Boundaries: The Danger of Invasive Species","description":"What are invasive species, and why are they dangerous? 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