What is the role of 4% dimethicone lotion in the treatment of pediculosis and pthiriasis (lice infestation)?

Updated: Aug 16, 2019
  • Author: Lyn C C Guenther, MD, FRCPC, FAAD; Chief Editor: Michael Stuart Bronze, MD  more...
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Dimethicone is available in the United States as an over-the-counter liquid gel formulation containing 100% dimethicone (LiceMD Pesticide Free) and in Canada and Europe as NYDA dimeticone 100 cSt Solution, 50% w/w. Dimethicone replaces the air in the breathing system of lice, nymphs, and nits (eggs); thickens quickly; and then causes suffocation and death. [39] Dimethicone can be used in individuals aged 2 years or older. LiceMD should be applied for 10 minutes; the hair is then combed with the included lice comb while LiceMD is still in the hair. Afterward, the hair is shampooed with regular shampoo and warm water. In contrast, NYDA is left on for 8 hours. After it has been on for 30 minutes, the dead lice and eggs should be combed out using the included NYDA lice comb. The hair should not be washed for 8 hours. Although NYDA should eliminate head lice after one application, the product monograph recommends a second application after 8-10 days to ensure complete removal of head lice. A small open-label US study showed that, after 14 days following 1-3 treatments with the 100% dimethicone gel regimen, 96.5% were free of live lice and 80.7% of viable eggs. [40] In another study, NYDA was found to be superior to 1% permethrin lotion. [41]

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