Itching
Head lice often cause the scalp to itch, although this is not always the case. Itching is not caused by the lice biting the scalp but by an allergy to the lice.
Some people are not allergic to head lice, so they may not notice that they have a head lice infestation. Even if someone with head lice is allergic to them, itching can take up to three months to develop.
In some cases of head lice, a rash may appear on the back of the neck. This is caused by a reaction to louse droppings.
Looking for head lice
Head lice are difficult to detect on the head, even when the head is closely inspected. Unhatched eggs or nits (empty eggshells) alone are not enough to diagnose an active head lice infestation.
This is because it can be difficult to distinguish between eggs and nits that are dead or alive. Nits also often remain glued to hairs after successful treatment.
In order to confirm an active infestation, a louse must be found through a reliable method, such as detection combing. Detection combing can be used to check more accurately for head lice. See Head lice - diagnosis for further information about this detection method.
