Prognosis
The typical course of head lice infestation is eradication with treatment, noting that a treatment requires 2 to 4 timed cycles to kill all hatching nymphs. The number of cycles depends on the product. Empty egg cases (nits) may remain on the hair shafts for months if not removed, and can be visible several centimetres from the scalp as the hair grows.
Recurrence
Nits alone do not represent a recurrence, and do not require treatment other than removal by hand or with a fine-toothed lice comb and washing the hair with a conditioner, if desired.
Recurrence of head lice infestation is not uncommon, and can occur for several reasons; the most common cause is improper use of the original pediculicide or other method resulting in self-re-infestation from hatching eggs that were not killed or picked/combed out. A second common cause would be re-infestation from a family member or other close contact that was not treated simultaneously with the index case. Re-infestation can also occur any time the index case comes into close contact with any other person with head lice infestation. None of these would necessarily indicate resistance to the original product.
If the original product/method is being used properly, and there are no further contacts with infested individuals, resistance to the product may be the cause of recurrence. An alternate product or method may need to be used, and the health care provider may need to be consulted.[10] Resistance is only documented for products with a neurotoxic mode of action.
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