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Persistent and Possibly Resistant Head Lice

2012 June 19

By Marcia Anderson

Another interesting case has crossed my desk: “Our second grade daughter contracted head lice when her best friend came to sleep over last fall. First we bought a lice elimination product, and began to treat her scalp.  We followed the directions, thought we had them licked, and then they reappeared the following month.   Next we tried another and an “electronic robi comb.” Three months later we still have lice. Now my youngest son has them.  There are prescription only products that contain Malathion  and another with Lindane that my pediatrician will prescribe that will perhaps work. Why do the over the counter products not work and should I put such harsh chemical pesticides on my children’s head?”

Before you resort to Malathion, know that some lice have a genetic mutation that leaves them immune to Malathion, however it is the inactive ingredient in the product, isopropyl alcohol, that seems to kill the lice. The lice products may contain pyrethrum, permethrin,  Lindane or Malathion as active ingredients; these are all pesticides that are meant to have residual properties that are potent enough to kill the lice that do not hatch for a few days.  Most pediatricians will not prescribe Malathion  or Lindane for treating children under six-years-old (as per directions on the label).  Lindane has been banned in the US for many agricultural purposes and also by the state of California and 17 European countries. I would think twice before I applied this to my own child’s head. Malathion was invented for pest control on agricultural crops and has been banned for indoor use as an insecticide. I would also think twice about using this pesticide on my child’s head.

Today’s lice are tougher and their exoskeletons are thicker than they used to be 20 years ago, when I too, had to treat my own children with head lice. I conducted some internet research and found that the lice of today hatch and mature on different schedules then they used to. This complicates established treatment directions. The lice seem to have also developed some resistance to the active ingredients, permethrin and pyrethrum. And forget turning your children’s heads into salad by slathering them with mayonnaise, lime garlic lotion or olive oil, as the little critters cannot be easily suffocated. (Journal of Pediatric Nursing)

Look for a product with isopropyl alcohol as a main ingredient and remember that it will take multiple treatment of lice products, to catch the next generation of lice as they hatch. If you are diligent and comb out the nits on a daily basis (such as every night during bath-time) you should be able to remove most of the nits between treatments.  In the mean time, wash and dry on high heat all hats, jackets, bed linens and stuffed animals.

About the Author: Marcia is the bed bug and vector management specialist for the Pesticides Program in Edison. She has a BS in Biology from Monmouth, second degree in Environmental Design-Landscape Architecture from Rutgers, Masters in Instruction and Curriculum from Kean, and is a PhD in Environmental Management candidate from Montclair – specializing in Integrated Pest Management and Environmental Communications. Prior to EPA, and concurrently, she has been a professor of Earth and Environmental Studies, Geology and Oceanography at Kean University for 14 years.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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