Download the journal article to learn about the continuing patterns of resistance and the specific gene mutations taking place in head lice.

The problem has been years in the making1:

  • 1945

    First natural pyrethrins used to treat lice

  • 1980s

    Use of Nix® over-the-counter (OTC) permethrin becomes common and is nearly 100% effective

  • 2000

    Lice in Florida and Massachusetts show signs of mutation and permethrin resistance

  • 2001

    Three pyrethrin- and pyrethroid-resistant gene mutations are seen in 37% of lice sampled from several states

  • 2009

    Nix® shows a decline to only 25% effectiveness

  • 2015

    The three pyrethrin- and pyrethroid-resistant gene mutations are observed in an average of 98% of lice gathered from 48 states, like these, shown 15 minutes after treatment with Nix® as compared to an untreated control group:

    Source: Videos created in collaboration with J. Marshall Clark, et al, and the Departments of Veterinary and Animal Sciences, Molecular Pharmacology, Microbiology, and Biochemistry and Molecular Biology at the University of Massachusetts, Amherst

How OTC Products May Compound the Problem

According to the EPA, pyrethrins and pyrethroids in pesticides are the second most common cause of symptomatic illness2, such as skin rashes, asthma-like symptoms and respiratory reactions like rhinitis, swelling of the mouth and larynx, coughing and wheezing.3,4 Yet, in most cases, small quantities of these pesticides are deemed safe when properly used. But the fact is, many patients don’t follow the instructions that accompany OTC products—which can lead to potential overuse and increased cost.5

Consider these statistics:

What You Can Do

The good news is that there are alternatives to pyrethrins and pyrethroids that are efficacious against head lice.

Still, it’s important to understand each product’s indications, warnings, precautions and usage instructions—many of them related to patients’ ages and existing medical conditions—before prescribing a new agent. When you discuss treatment plans with your patients, consider the information in this chart and consult the full safety and prescribing information for these products at Daily Med.

Download Chart
I tell parents, if you suspect it’s head lice, contact your healthcare professional. We don’t want them treating dandruff or glitter with these agents and contributing to resistance. If they see creepy, crawly adult lice the day after treating with permethrin the first time, we move on right away to a new agent. Chris Belcher, MD, Peyton Manning Children’s Hospital at St. Vincent, Indianapolis, IN

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