Dead eggs and eggshells (nits) may remain firmly attached to the hair for at least eight months. Human hair grows from the base about 1 cm per month. The affixed nit is thereby carried away from the scalp as the hair grows. Nits become more noticeable as they are moved away from the scalp. The contrast afforded by dark hair accentuates the likelihood of their detection. The discovery of “eggs” several months after the last treatment can lead to a mistaken conclusion or “false positive diagnoses” of infestation. Mechanically removing nits is time-consuming. When using fingernails to remove nits from the hair, it should be taken into consideration that some of the nits are firmly attached and trying to remove them could tear apart the hair or worse remove the hair from its base (follicle) causing a local damage to the skin. Cutting the hair with a scissor under the area where the nit is attached, could prevent such damage. 

Removal of nits with a louse comb is easier when the hair is wet with water or after shampooing or even better after use of a conditioner. Hair conditioners make the combing of the hair and the removal of the nits easier, as the hair become more slippery for the glue which attaches the nits on the hair. However, these methods are not suitable for removing freshly laid eggs and should be repeated weekly for several weeks. It is also possible few weeks after having removed most of the visible nits, “new eggs” appear on the hair, giving the impression that the person was re-infested, however, it should be taken into consideration, that those nits were earlier closer to the scalp and accordingly invisible and now that they move away from the base of the hair can be easily seen. Although several formulated products are claimed by their manufacturers to dissolve eggs or the glue that affixes the eggs to the hair, data to support such claims are lacking.  

Generally, louse eggs found more than 1 cm from the scalp are unlikely to be viable. The removal of dead eggs and empty eggshells is not essential for therapeutic reasons but is sometimes done for aesthetic reasons and to avoid that people in the environment of the child think that he/she is infested with lice.