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Facts of Lice

The Itsy-Bitsy Bad Guy

New guidelines published by the American Academy of Pediatrics (AAP) have brought attention to a tiny nuisance we all dread – head lice. Nothing can make a rational adult crazier than the mere mention of these pests. Just the thought makes your scalp crawl. Thus, AAP recommendations that schools abandon no nit policies and allow children with head lice to stay in the classroom have sparked controversy.

Head lice affect 6 to 12 million children nationally each year. They are approximately the size of a sesame seed and usually grayish white. They move quickly and avoid light, making them hard to spot. Itching, the hallmark symptom, is caused by scalp sensitization to lice saliva. Itching may not occur in new cases for four to six weeks so the infestation may go unnoticed. Nits or egg casings are easier to spot than head lice and are most often found behind the ears or at the back of the neck. Nits, unlike dandruff, hairspray or debris, attach firmly to the hair shaft close to the scalp. You can easily brush away the latter, but not so the nits.

Treatment usually begins with over the counter pediculocides such as permethrin 1 percent or pyrethrins. Follow the instructions closely. If advised to apply product to freshly washed hair avoid conditioning agents as they can impair the product’s adherence to the hair shaft. Rinse products over a sink with warm water to limit skin exposure. As most products do not kill eggs, experts recommend routine retreatment on day nine. An alternative schedule is to treat three times: on day one, seven, and thirteen. In areas where resistance to store-bought products is documented, or if careful treatment has failed, there are several therapies available by prescription. Occlusive therapies such as petroleum jelly or Cetaphil on the hair have not been well evaluated, but may be a treatment option for younger patients or for families who do not wish to use a pediculocide.

Removing nits does not prevent spread but may decrease over-diagnosis and unnecessary spending for retreatment. Carefully combing wet hair with a fine toothed comb can loosen nits. Products that damage the nit adherent may also damage the hair shaft. Some products that loosen nits may also interfere with the effectiveness of permethrin.

Head lice are almost always spread by head to head contact. While some recommend treating family members who share a bed with the infested person, there is no advantage to treating everyone without evidence of infestation. Cleaning items that have come in contact with the infested person in the last 48 hours is recommended at temperatures greater than 130°F. Furniture, carpets, and carseats can be vacuumed. A louse can’t jump, hop or fly, and on its own, will usually die in about 48 hours unless it finds a human host.

Head lice have low contagion within classrooms. Children with head lice may have been at school for weeks before the diagnosis is made, so excluding them makes little sense. Only live lice can cause infestation, so no nit policies stating that children cannot return to school until all nits are removed should be abandoned.

Is there good news about head lice? While a nuisance, they do not spread disease or cause any health hazards.

Laura Duke
Laura Duke, CPNP, is a pediatric nurse practitioner and lactation consultant at Pediatric Associates of Richmond, Inc. She is the mother of three girls.
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