Head lice, or pediculosis, is most common in children, though adults get them also. On average, 10 million people a year in the U.S. will seek treatment for lice. These parasites are a different species than those that infest other parts of the body. Head lice live exclusively on the scalp.
So Where does Hair Lice Come From?
Lice have been a human parasite for thousands of years, and are well documented in history. Today, most children get lice from schoolmates or in daycare settings and then pass on the infestation at home. Lice have a three part life cycle.
As nits, they are extremely small, and are often mistaken for dandruff. Once they have become nymphs, they are more visible, and itching or feelings of movement on the scalp may be felt, though people with thick hair often don’t experience symptoms.
Most spreading occurs during the early adult stage, when the lice are the most active. Lice don’t “jump” from person to person, they crawl down the hair and often onto the clothes to another host, or migrate through direct head to head contact. Adult lice then lay their eggs along the base of the hair shaft, and in severe infestations or thick hair, the clumps of eggs will be noticeable where the hair meets the scalp and along the hair shaft.
As adults, lice will migrate from one person to another, and this is most common in crowded conditions and among young children. When children play close together or their heads are in contact, lice can spread rapidly.
The eggs can be spread by bed linens, towels, clothing, brushes and combs, and by sharing hats with someone who is infected. Lice can only live 48 hours without blood, so sealing potentially infected toys in plastic bags for a few days will generally kill any that have left the infected host, though washing potentially contaminated materials is preferred to prevent further spreading and re-infection.
On the scalp, however, lice can live up to two weeks, and are laying eggs their entire adult phase, which is why outbreaks in schools can last for so long. By the time signs are visible, others in the home or classroom have already been infected, and children will frequently be re-infected when they return to school. Because head lice are extremely contagious, it is important to watch for early signs of lice and control the condition as soon as you find it to prevent spreading and continuing infection.
Lice aren’t harmful, and they carry no diseases. However, people who scratch frequently not only spread them easily, but also irritate the skin and secondary infections can form in any open scratches. Once someone is infected, prompt treatment of the head and sanitizing items the person has been in contact with can help prevent further spreading.