The most common way to suspect head lice, is that your scalp itches. The itching is a reaction to
the saliva of the head lice which they leave in the spot, where they have sucked blood. The extent of itching depends on how long you have had the head lice and how many there are.
If you have not had head lice before, it may take some four to six weeks before you start itching, and during his period head lice may easily be passed on to others. In case of recurrent infestations, it usually takes no more that 24 to 48 hours until a host reacts to the saliva of the head lice.
Therefore, itching is a very poor indication as to whether someone is infested with head lice or not. Consequently, combing is the best way to make an early diagnosis and prevent the infestation to spread to others. Thus, it is important that both children and adults at risk of being infested with head lice are regularly checked with a proper lice comb.