Head lice infestation

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at July 23, 2016
StartDiseasesHead lice infestation

Pediculosis or lice infestations have a significant social stigma. A head lice infestation has frequently been seen as associated with poor hygiene and poverty, even though these types of infestations do not pose any kind of a major health problem. Nonetheless, people go to great lengths to prevent infestations. In recent years, head lice have been found to have developed resistance to many traditional chemical treatments. Nevertheless, head lice infestations are both highly preventable and highly treatable.


Definition & Facts

Technically, head lice are a type of insect and human parasite, using human hair as a viable environment in which to live and propagate. Hair follicles are particularly inviting for lice which use hooked claws to move around and relocate on a host. The lice feed off of the human by making very small incisions into the skin and digest the resulting blood flowing from the wound.

There are several different kinds of lice infestations including public lice which infest the pubic hair and is often a sexually transmitted disease and body lice. Head lice can be found in just about every part of the world where there are humans, and they tend to spread more easily the more densely people are located next to each other. Such locations for easy transmission include refugee camps, nursing homes, homeless populations, schools, and military units. An original rationale for requiring short haircuts among military personnel was to prevent head lice infestations.

Symptoms & Complaints

Head lice can become noticeable to a person as a sensation of something small running along the scalp as well as general itchiness. The bites caused by the feeding lice tend to cause irritation which in turn creates the itchiness.

When the host begins scratching, the wound can become infected from repeated tearing of the skin into which bacteria enter. That in turn can create sores. In the meantime, the lice reproduce, lay eggs, and increase their number, which repeats the cycle and creates more wounds, more scratching, and more sores if left untreated.

Head lice generally do not migrate to other parts of the body except the eyebrows. The insect is designed to stay in the hair of the person, unlike other types of lice such as body lice which live in a person's clothes and only move to the body to feed. 


Lice has long been associated with poverty and poor hygiene and thus has a social stigma. However, a lice infestation often has nothing to with cleanliness. Instead, the infestation occurs when one person’s hair is close enough to make contact with another person who has lice. Naturally, the lice then spreads among close-knit families or those living in close quarters and close proximity to each other. As the lice lays more eggs on a new host, the number of lice increases which increases the risk of infestation for others.

Diagnosis & Tests

The most common way of diagnosing a head lice infestation involves a close examination of a person’s scalp. This is done by using a very fine comb to move through one slice of hair after another. The examination involves looking for one of three phases of lice: adult, juvenile louse, or the nit (egg). The lice themselves may not always be visible as they can move to avoid detection.

Adult lice typically look like a small sesame seed, but they are hard to remove because they can quickly move and disappear out of sight into the hair. However, the eggs are planted on the hair follicle and remain stationary. Even when hatching, the egg shells stay connected and are easy to find with a bright light and careful inspection. These then are a sure giveaway that an infestation is present on a host and treatment is needed. The confirmed patient may be isolated from others to prevent further transmission.

Treatment & Therapy

Treatment for head lice traditionally requires a lice-killing chemical or solution. There are both over-the-counter medicines as well as prescription alternatives that are provided by a dermatologist. In either case, the treatment takes a number of days as medication attacks the lice at different stages in its life cycle. This then allows adult lice to die off and prevents the production of new eggs that would create new lice.

The treatment is applied like a shampoo and left in wet hair to soak in. Then the hair is run through methodically with a fine lice comb to catch and remove the dying or dead adult lice. The patient then has to be examined 12 hours later to determine if there was an effect. If not, then the first medicine used is not working. If it works, the medicine is left in the hair for usually two days and then checked again.

The main ingredient for most lice medicines tends to be malathion. However, two alternatives include lotion containing benzyl alcohol and lindane. Both can cause skin irritation and can be flammable, so conscious care when applying treatment is a necessity.

Prevention & Prophylaxis

One of the best ways to prevent lice is to stay away from close contact with anyone who potentially has lice in the first place. Of course, for people who live in close quarters this is not always possible.

Regular inspections of schools, nursing homes, and other densely populated institutional settings can help quickly identify infestations and prevent more widespread infestations. The Centers for Disease Control and Prevention does not advocate a no-nit policy for schools. If the lice can be found quickly, early treatment can stop the progression before it gets out of hand.

Because an average treatment runs at least one week to nine days and a child may be told to stay out of school for the treatment duration until he or she is rid of the lice per inspection, arrangements of care are often necessary in the meantime.