Itching may take
four to six weeks to develop the first time a person has head lice.
Head Lice Symptoms
Many people with head lice have no symptoms. Others may feel a tickling feeling on the scalp or in the hair, itching (caused by the bites of the lice), irritability and difficulty sleeping (because lice are more active in the dark) and sores on the head (caused by scratching, which can sometimes become infected).
Itching, the most common symptom, may take four to six weeks to develop the first time a person has head lice. In some first-time cases, symptoms may not develop at all. Subsequent infestations can produce symptoms in 48 hours or less.
Head lice are not dangerous and do not transmit disease.