Head lice are parasites that can infect humans of every socioeconomic class. Their diet consists of human blood, and they lay their eggs, or nits, close to the food source to allow their young to feed as soon as they hatch. The nits will be found securely attached to the hair close to the scalp. If lice remedies have been used on an infected person, it may be difficult to know if the nits are holding live lice or if they have been effectively killed.
Turn the nit so the profile is visible through the magnifying glass. If a nit has hatched, the top, called the operculum, will be gone. The operculum is the soft part of the nit where the louse will escape after gestation. The nit will maintain its oblong shape, but it will have a flat top. If the nit is still a full oval, it is alive and it should be removed and crushed between the fingernails. If the nit is dead, it will have collapsed into itself, and the sides will look crumpled.
Check the colour of the nit. Live and dead nits are brown; hatched nits are clear. If the colour is brown, remove the nit right away and crush it between the fingernails before placing it in a plastic bag. Dispose of the plastic bag immediately.
Squeeze any nits removed from the head to check the pressure inside the nit. Live nits will pop when squeezed; dead nits will do nothing. Make sure every nit found is dead after treating the hair for a head lice infestation.
A lice infestation can recur if a live nit is missed and left in the hair. Be sure to check the hair thoroughly, section by section, with a fine-tooth comb, searching for any tiny nits and removing them. Be sure to kill the nits, as they can survive in carpets and will hatch, possibly reinfesting the home.