Overuse of Lice Control Chemicals

Persistent infestation was the concern of a county task force, defining "persistent lice as three incidents of live lice over a 6-week period", but the panel was also concerned about the risks of chemical pesticide exposure. Literature review identified factors that contribute to overuse of chemical pesticides for persistent lice.

Inadequate safety information was considered the absence of information accompanying commercial products about how many times or how often a product could be safely used. Given the non-prescription status, caretakers may assume repeated use is safe. The readability of instructions was found to be 8th to 10th grade levels, too high for many users, and lacking simple pictures to show safe use, e.g., exposure time, rinsing over a sink.

The "kill time" for lice (pediculicide/POISON) products can vary from 10 minutes to hours, but an effective product will kill lice (not nits) within its recommended application time if the concentration and saturation are as directed. Increasing time beyond the recommended duration does not increase its effectiveness. (Note: resistant lice and/or nits are simply not killed by these pediculicide POISONS.)

Misdiagnosis of lice and attempts to determine the viability of nits underscored the recommendation to remove nits as part of initial treatment. One study suggested that in warm climates, viable nits are found further than one-fourth inch from the scalp - considered by some to indicate an empty egg case.

Rinsing lice shampoo in a shower or tub was seen as an unnecessary skin exposure to pesticide. Consumers view the product as a "medicated" shampoo, not a pesticide. The product ought to be rinsed over a sink to limit skin exposure, but only one product included this in its directions or suggestions.

Prophylactic use of lice shampoos is an inappropriate response except within the FDA approval of the permethrin-based product. However, the definition of "epidemic" is unclear, and preventive treatments may increase the risk of lice resistance as well as chemical overexposure. Lice treatment products should be stored out of reach of children, as with any pesticide, not with the household shampoos typically within children's access. (Gordon S. J Sch Nurs 1999;15(5):6-9)