Head lice are parasites, commonly diagnosed in children ages 3 to 12 years of age, although they can affect all segments of the population. The adult louse is about the size of a sesame seed, and can live up to 4 weeks. The adult louse lays nits (eggs), firmly attached to the hair shaft with a glue-like substance, approximately ¼ inch from the scalp. Viable nits are typically camouflaged to match the pigment of the affected person's hair color. They are best seen at the nape of the neck, behind the ears, and at the crown of the head. Empty nits, i.e., no longer viable, are easier to see, as they appear white in color.
Nits incubate for 10 to 14 days. Once hatched, the young louse, or nymph, grows another 9 to 12 days, at which time they can mate, and the female will lay her nits. Head lice typically live for less than 1 day away from the scalp at room temperature. Nits cannot hatch at a temperature lower than that on the head.
Head lice cannot jump or fly; they crawl. Most cases of transmission occur through head to head contact with another affected individual. Less likely spread of head lice may occur through contact with personal items belonging to an affected individual.
It is recommended that parents inspect their child's head regularly, every 7 to 10 days. Dividing the child's hair into segments with the use of clips, and then combing through each area with a fine toothed comb is an effective method of inspecting the head. This should be done in a well-lit room. Crawling lice confirms the diagnosis. Nits found firmly attached within ¼ inch of the base of hair shafts suggests that the individual has an active case of head lice. Nits that are found more than ¼ inch from the base of the hair shaft are almost always non-viable, and do not require treatment.
When an individual is diagnosed with head lice, all close contacts should be inspected. All affected individuals should be treated at the same time. Daily inspection of the head to remove nits and lice should continue for the next 7 to 10 days. Retreatment after 7 to 10 days is then recommended, as there is no treatment that completely kills all eggs. It is essential that the label directions be closely followed. Products may vary as to how they should be used.
Supplemental measures within the home environment should be taken to avoid reinfestation by lice. These measures include washing the affected person's clothes, towels, and bedding used during the 2 days prior to treatment. Wash in hot water, and dry on hot heat. Any items that cannot be washed should be sealed in a plastic bag for 2 weeks. Personal items used for hair grooming should be washed in hot water for 5 to 10 minutes. Vacuum the floor and furniture used by the affected individual. Primary treatment should be concentrated on the person's head. As stated above, head lice typically survive less than a day off the head and cannot feed, and nits cannot hatch at a temperature lower than that on the head.
The following links are excellent sources of information regarding the etiology, diagnosis, prevention, and treatment of head lice. For questions and clarification of information, please contact Janice Heckman, RN, district nurse at your child's school.
The Harvard School of Public Health Document and information:
http://www.hsph.harvard.edu/headlice.html
The Centers for Disease Control and Prevention fact sheets and information on head lice:
http://www.cdc.gov/lice/
The American Academy of Pediatrics Resources and Document:
The 2002 policy: http://aappolicy.aappublications.org/cgi/content/full/pediatrics;110/3/638
