Head Lice

  • About:  The head louse, or Pediculus humanus capitis, is a parasitic insect that can be found on the head, eyebrows, and eyelashes of people. Head lice feed on human blood several times a day and live close to the human scalp. Head lice are not known to spread disease.  An adult head louse is about the size of a sesame seed, has six legs, and is usually tan or grayish-white in color.  A mature female louse can lay up to 10 eggs per day.  These tiny eggs (nits) are attached firmly to the base of the hair shaft within about 4 mm of the scalp.  The eggs typically hatch within 7-12 days.  


    Head lice do not jump or fly, but rather move through the hair by crawling.  Movement of the lice through the hair causes the itching associated with an infestation.  In almost all cases, infestation occurs through direct contact. Indirect infestation is much less likely, but children should be taught not to share personal items such as brushes, combs, and hats,  Lice do not carry disease and are not a sign of poor hygiene.  


    Treatment:   The best way to avoid a chronic problem is to perform regular checks of all family members.  Infestations should be treated promptly and completely.  The American Academy of Pediatrics and the California Department of Public Health recommend treatment with over-the-counter products containing permethrin or pyrethrins, such as Nix or Rid medicated shampoos.  After using the product according to package directions, follow-up with nit removal and wet combing.  Re-check and remove nits frequently until hair is clear.Eggs will not hatch once off the head, and an adult louse can only survive for about 24 hours away from the scalp.  For these reasons, excessive housecleaning following an infestation is not necessary.  Clothing and bedding recently used should be washed and dried.  Thoroughly vacuum carpets.  Stuffed animals and pillows can be put in the clothes dryer on high.  Home "lice sprays" have not been proven effective.  


    Lice & Attendance:  Student with head lice should miss school only for the time required to properly treat the infestation.  It is the policy of the Mill Valley School District that students found to have live lice will be excluded from attendance until treated.  Once treated, the student can return to school.  If only nits are found upon examination, the student may remain at school at the discretion of the school office or district nurse.

    Sources:  American Academy of Pediatrics Clinical Report on Head Lice (May 2015) and Mill Valley School Board Policy 5141.33

    Head Lice Information for School Attendance

    Students diagnosed with live head lice do not need to be sent home early from school; they can go home at the end of the day, be treated, and return to class after appropriate treatment has begun. Nits may persist after treatment, but successful treatment should kill crawling lice.

    Head lice can be a nuisance but they have not been shown to spread disease. Personal hygiene or cleanliness in the home or school has nothing to do with getting head lice.

    Both the American Academy of Pediatrics (AAP) and the National Association of School Nurses (NASN) advocate that “no-nit” policies should be discontinued. “No-nit” policies that require a child to be free of nits before they can return to schools should be discontinued for the following reasons:

    • Many nits are more than ¼ inch from the scalp. Such nits are usually not viable and very unlikely to hatch to become crawling lice, or may in fact be empty shells, also known as ‘casings’.
    • Nits are cemented to hair shafts and are very unlikely to be transferred successfully to other people.
    • The burden of unnecessary absenteeism to the students, families and communities far outweighs the risks associated with head lice.
    • Misdiagnosis of nits is very common during nit checks conducted by nonmedical personnel.

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