Lice are becoming invincible in America.

A study out of Southern Illinois University-Edwardsville found that  lice have developed a resistance to medications available over-the-counter in at least 25 states. While the press release didn’t mention Colorado, it’s best to be extra mindful going with kids returning to school.

Out of 109 lice population samples, 104 had high levels of gene mutations commonly linked to the resistance of insecticides called pyrethroids, which include the active ingredient permethrin.

This doesn’t mean lice treatments won’t work – you’ll just need a higher dose or treatment that lice aren’t resistant to, which a doctor can easily prescribe. What you do want to avoid are home remedies like olive oil and mayonnaise or fine-toothed combs. If all else fails, though, you can always shave your head.

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