Head lice should not be considered as a medical or public health hazard and are not known to spread disease. Although annoying because their presence may cause itching and loss of sleep, and gross because they live in peoples hair, they are relatively harmless. Sometimes the itching can lead to excessive scratching that can sometimes increase the chance of a secondary skin infection.

What are the symptoms of head lice?

Itching (“pruritus”) is the most common symptom of head lice infestation and is caused by an allergic reaction to louse bites. It may take 4–6 weeks for itching to appear the first time a person has head lice.

Other symptoms may include a tickling feeling or a sensation of something moving in the hair;
irritability and sleeplessness; and sores on the head caused by scratching. These sores caused by scratching can sometimes become infected with bacteria normally found on a person’s skin.