This information is provided by the North Dakota Department of Health. It is not a substitute for advice from your doctor.
What are head lice?
Head lice are tiny insects that live on the human head and feed on human blood. They multiply rapidly, laying little white to yellow-colored, oval-shaped eggs (called nits) that they glue to the base of the hair, close to the scalp. Unlike dandruff or lint, they will not wash, blow away or be removed easily.
The adult louse (singular form of "lice") is flat and wingless; it does not have the ability to fly, hop or jump. Lice tend to adapt to their surroundings (hair and skin color), so they range in color from red, brown or black to gray-white and are often hard to see. A louse is very small (about 1/8 inch in length), and has six legs, a diamond-shaped head and an elongated body.
Who gets head lice?
Anyone can get head lice, regardless of age, race, social-economic status or hygiene practices.
How are head lice spread?
Lice cannot fly, hop or jump. They usually are transmitted by contact with an infested person or by the clothing or personal item used by an infested person. Household items such as furniture, carpeting, bedding, towels or upholstered car seats also may be a source of transmission. Head lice do not feed or live on household pets. Head lice do not spread disease.
When and for how long is a person able to spread head lice?
As long as they are infested. Even after treatment, a daily head check for lice and/or nits is recommended for at least seven to 10 days.
Does a past infestation make a person immune?
No. A person can get head lice more than once.
What are the symptoms of head lice?
Itching of the head is the most common sign; however, some people who have head lice have no signs. Itching occurs when lice bite and suck blood from the scalp. Itching may be from slight to severe. The amount of itching that occurs is often dependent upon the degree of infestation. Itching may be very mild if the infestation has just occurred or it may be severe if the infestation has gone untreated for a long time.
Other symptoms may include sores on the head from scratching, a tickling feeling of something moving in the hair or sleeplessness (lice like the dark and are more active at night).
What complications can occur?
In severe and/or chronic cases, a person may develop infected sores and/or swollen glands in the neck or under the arms. If this occurs, the person should contact his/her health care provider.
What can be done to control the spread of head lice?
Instruct children not to share coats, hats, scarves, combs, brushes, barrettes or any other hair ornaments. Check the heads of every family member on a regular basis.
When an infestation of head lice is found, it should be reported to anyone who has had close contact with that person over the previous week so any other cases can be found and treated.
No head lice treatment product is 100 percent effective. It is essential that all lice and nits be removed after head lice treatment. When treating someone for head lice, read and follow all manufacturer's recommendations and directions on the product label.
Head Lice Life Cycle
Eggs (commonly called nits)
Nits are laid by the adult female and attached to the hair shaft by a glue-like substance produced by the louse. Nits are oval or teardrop-shaped and range in color from white to yellow to tan to grayish in color, depending upon the stage of development and whether they have hatched or been killed by treatment.
Stage 2: Nymphs (immature louse)
The nits incubate for about seven to 14 days, then hatch to release a nymph. During the next seven to 10 days, the nymph continues to grow and mature, going through three molts, until it becomes a full adult louse.
Stage 3: Adults
The adult louse is about the size of a sesame seed and has a life span of about 30 days. The female is larger than the male and can lay three to five nits per day, or up to 150 nits during her life span. The adult louse needs to feed on blood every three to six hours and can usually survive for no longer than 24 to 36 hours away from the human host.