Lice

Introduction

Have you or someone in your family ever had lice? If you have, you know what a hassle it can be to get rid of them. If you haven?t experienced a lice infestation, consider yourself lucky because it?s been estimated that millions of people around the world have lice each year and don?t even treat it! Are you at risk?

What is it?

Much to many parents' annoyance, the head louse is a tiny, wingless parasitic insect that lives among human hairs and feeds on extremely small amounts of blood drawn from the scalp or skin. These little creatures are known as Pediculus humanus capitis (a head louse), and Pediculus humanus corpois (a body louse). Although they may sound gross, lice (the plural of louse) are a very common problem, especially for children ages 3 years to 12 years.

Lice eggs, known as nits, are laid and ?glue? themselves to the base of hair strands. Nits look like tiny white specks on the hair strand. It takes 7 to 10 days for the eggs (or nits) to hatch and within 2 weeks of hatching, they develop into mature lice. Lice can grow to be 2 to 4 millimeters in length (about the size of a sesame seed). If not properly treated, mature lice go on to lay more eggs (nits) and populate at an alarming rate.

Lice are not usually dangerous and they usually do not spread disease, but they are very contagious and can be downright annoying. Their bites may cause a person?s scalp to become itchy, flaky, and inflamed. Continuous scratching may lead to skin irritation and even infection.

Several types of lice exist:

  • Head lice? This is the most common type. These lice develop on the scalp. They are easiest to see around the sides of the neck and over the ears. Small nits produced by lice attach to the hair shafts.

  • Body lice? These lice spend most of their time in the seams and folds of clothing. Body lice are often spread by direct contact with infected clothing or bedding or with an infected person. In rare cases, body lice may carry diseases, such as typhus and malaria.

  • Pubic lice? Commonly called crabs, these lice occur on the skin and hair of genital areas but they can even be found on stomach and armpit hair and on eyelashes. Sexual contact or contact with infected clothing or bedding can spread pubic lice.

What causes it?

Lice are spread only by direct contact with an object or person infected with lice or their eggs. Eggs hatch in about one week. Lice can't fly or walk on the ground and they typically die after losing contact with the human body for two days. They spread by:

  • Head-to-head or body-to-body contact. This may occur as children or family members play or interact closely together.

  • Close proximity of stored belongings. Storing clothing next to each other in closets, lockers or on side-by-side closet hooks at school, or storing personal items such as pillows, blankets, combs and stuffed toys in close proximity at home can permit lice to spread.

  • Sharing items. These may include clothing, headphones, brushes, combs, hair decorations, towels, blankets, pillows and stuffed toys.

  • Contact with contaminated furniture. Lying on a bed, or sitting in furniture can spread lice. Head lice live for up to two days off the body.

  • Sexual contact. All three forms of lice can spread in this manner.

Who has it?

Although the incidence of head lice occurs in children most often, lice can appear in anyone's hair, no matter what hair length or the person's degree of cleanliness. It is a common misconception that having long or uncleanly hair increases the likelihood of infestation. In fact, length and/or cleanliness of hair have no effect on the risk of developing a lice infestation. Lice are seen less often, however, in African Americans due to the texture of their hair. Lice have difficulty gripping or holding on to this type of hair.

Body lice are more often seen in impoverished conditions?in individuals who have poor personal hygiene or those who are homeless or living in overcrowded, unsanitary conditions.

Pubic lice can occur in anyone, especially individuals who are sexually active. Condoms do not protect against pubic lice.

What are the risk factors?

Risk factors are characteristics that can predispose you to developing a condition. The following are key risk factors for contracting lice:

  • Living with a person who has lice
  • Regularly sharing hair accessories
  • Living in crowded conditions (such as in a care facility or dormitory)

Children between the ages of 3 and 12 are at the highest risk for contracting lice. This is generally due to the fact that they spend a lot of time in close quarters with other children. Women are also at increased risk for lice, because they are more likely to share infected hair accessories.

What are the symptoms?

While lice infestations do not usually cause illness, there are certain signs and symptoms to look for:

  • Lice?The physical appearance of lice on the scalp, the body (pubic or other body hair), and clothing may look similar to tiny fruit flies. Lice are a rusty yellow color, and can be up to 1/8 inch (2 to 4 millimeters) in size.

  • Nits?Nits resemble tiny flower (willow) buds. Nits can be mistaken for dandruff, but unlike dandruff, they can't be easily brushed out of hair.

  • Louse droppings? Droppings look like a fine black powder and may be seen on bed linens.

Additionally, in some individuals, a lice infestation can cause itching and a rash, which is often worse behind the ears or on the back of the neck (for head lice), in genital areas (for pubic lice), or wherever lice is on the body. Small red bumps may appear where lice have bitten the skin.

How is it treated?

The goal of therapy is to eradicate the lice and their eggs and provide symptomatic relief to patients.

Available Treatments:

  • 1% permethrin (Nix), available over-the-counter, is the drug of choice for all 3 lice infections (body, head, and pubic lice). The cure rate is reported to be in the range of 90-97%
    • Side effects of this medication include itching, stinging, and tingling.
    • Application: Apply to scalp after hair has been dried following a shampooing. The scalp should be saturated with permethrin liquid, and a towel should be wrapped around the scalp to allow the application to stay on for 10 minutes. Rinse hair after 10 minutes.
    • May need to repeat the application.

  • 1% permethrin cream mix (Nix-Creame Rinse) is also available. Side Effects and application technique is the same as for the 1% permethrin.

  • Pyrethrins?(e.g. Rid, Triple X) - are natural extracts from the chrysanthemum flower. Though safe and effective, pyrethrins only kill crawling lice, not unhatched nits. A second treatment is recommended in 7 to 10 days to kill any newly hatched lice. Treatment failures are common.

  • 0.5% malathion (Ovide) is a prescription medication that is effective at getting rid of lice. The application should be left on the scalp for at least 90 minutes. Because it has a high alcohol content, it is highly flammable and can cause difficulty breathing if accidentally ingested. For these reasons, it should only be used for resistant cases of head lice.

  • 1% lindane shampoo is available only by prescription. It should be used cautiously and only if a first-line treatment has failed or cannot be tolerated because lindane shampoo can be absorbed through the skin and cause serious side effects including seizures. The risk for serious side effects is increased when lindane shampoo is used improperly. Lindane Shampoo should also be used with caution in infants, children, the elderly, individuals with other skin conditions, and those who weigh less than 110 lbs (50 kg) as they may be at increased risk for serious problems such as nerve and brain damage from any lindane absorbed through the skin. Proper use in appropriate individuals can help to avoid the potentially serious side effects associated with lindane shampoo. The FDA now requests that a medication guide explaining the proper use of lindane be dispensed with every lindane prescription. Ask your pharmacist for a medication guide if one did not accompany your prescription for lindane shampoo.

  • An ocular lubricant (Lacri-Lube S.O.P), available over the counter, is useful in removing crab louse infection of the eye lids. This medication is applied twice daily.

  • Calamine lotion with 0.1% menthol may be used for the relief of itching. It can also be found over the counter.

Helping Yourself

  • Comb wet hair. Use a fine-toothed or nit comb to physically remove the lice from wet hair. Repeat every three to four days for at least two weeks. This method may be used in combination with other treatments and is usually recommended as the first-line treatment for children under age 2. Remember to soak combs and brushes for 1 hour in rubbing alcohol, Lysol, or wash with soap and hot (130?F) water before each use.

  • Although rare, lice can develop resistance to medication therapy. In this case, physically removing the organisms may be tried, but if the infestation lasts longer than 3 days, you should contact your doctor for further assistance. A good way to determine if there is resistance is to see if the head lice medication does not kill any crawling lice within 24 hours. If lice are still crawling within 24 hours of the medication application, then resistance is likely. If the medication kills some of the lice or the lice are only twitching (but not crawling) 24 hours after treatment, then resistance to medication is probably not occurring.

  • Consider treating family members, sexual partners, or anyone who could have come into contact with the lice.

  • All bedding and clothing should be sterilized by boiling or washing in the hottest water cycle of the washing machine to avoid reinfestations. Vacuuming floors and furniture can help in removing lice but only vacuum the places where the infested person usually sits or lays. (Vacuuming in other areas can spread the lice.)

  • Seams of clothing should be examined to verify that all organisms are removed. You should dry clean clothes that are not washable such as hats and coats.

  • Do not treat the infested person more than 3 times with the same medication if it does not seem to work.

  • Do not use extra amounts of the lice medication unless instructed. These drugs are insecticides and can be dangerous when misused or overused.

  • Do not mix head lice drugs unless instructed by your doctor.

  • Household sprays should not be used to kill lice infestations because breathing the fumes of these agents is dangerous.

    It is very difficult for head lice medication to penetrate the nit shell. Medication may effectively kill crawling bugs, but may not treat the nits. Therefore, follow-up treatment is recommended.

    What is on the horizon?

    In resistant cases of lice, combining permethrin therapy with an antibiotic known as trimethoprim/sulfamethoxazole (TMP/SMX) may help kill the lice. In recent studies, a combination of 1% permethrin and TMP/SMX was an effective therapy for head lice infestation. Thus far researchers have recommended that the dual therapy with 1% permethrin and oral TMP/SMX be used in cases of multiple treatment failures or suspected cases of lice-related resistance to therapy. More research is currently being done on the use of antibacterial agents in response to lice resistance.

    1% lindane shampoo was a popular pesticide used for head lice, but now after some convincing research, lindane has many adverse effects compared to the permethrin treatment. Some major adverse effects include neurological disorders such as seizures (mostly due to absorption of lindane through the scalp or skin) and skin irritations. Although lindane is still in the market, current research is discouraging the use of this product, and the FDA has recommended a medication guide be dispensed with the shampoo describing how proper use can help prevent some of the undesired adverse effects.

    Due to increasing drug resistance, researchers are changing the direction of their studies. Current studies are focusing on the nit sheath, which is the glue that holds the lice nit to the hair, and the actual nit-laying process. Further understanding in these areas may lead to the development of improved treatment options.

    References

    DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, editors. Pharmacotherapy: A Pathophysiologic Approach. 6th ed. New York: McGraw-Hill; 2005: 2075-2076.

    HeadLice.Org for Kids. Available at: http://www.headlice.org/kids/index.htm. Accessed July 24, 2007.

    Centers for Disease Control and Prevention (CDC). Available at: http://www.cdc.gov/ncidod/dpd/parasites/lice/default.htm. Accessed July 24, 2007.

    Burkhart CG. Relationship of treatment-resistant head lice to the safety and efficacy of pediculicides. Mayo Clin Proc 2004:79:661-666

    Hipolito RB, Mallorca FG, Zuniga-Macaraig ZO, et al. Head lice infestation: single drug versus combination therapy with one percent permethrin and trimethoprim/sulfamethoxazole. Pediatrics 2001 Mar; 107.

    Yoon KS et al. Permethrin-resistant human head lice, Pediculus capitis, and their treatment. Arch Dermatol 2003; 139:994.

    Dodd CS. Interventions for treating head lice. Cochrane Database of Systematic Reviews (3). Oxford: 2002.

    Pollack RJ, et al. Differential permethrin susceptibility of head lice sampled in the United States and Borneo. Archives of Pediatric Adolescent Medicine, 153: 1999, 969?973.

    Phillip K. Peterson, M.D. Emerging Neurological Infections. Neurological Disease and Therapy. Volume 353:2092-2093, 2005.

    E-Medicine Consumer Health. Available at: http://www.emedicinehealth.com/lice/article_em.htm. Accessed July 24, 2007.

    Treating Lice Infestation Fact Sheet: Available at: http://www.cdc.gov/ncidod/dpd/parasites/lice/factsht_head_lice_treating.htm. Accessed July 24, 2007.

    Bergman JN and Malcolm CE. Trying to keep ahead of lice: a therapeutic challenge. Skin Therapy Letter. 2006 Dec-2007 Jan;11(10):1-6

    Lindane facts: the truth about lindane. Available at: http://www.lindane.com. Accessed July 30, 2007

    Lice Health Condition Last Updated: July 2007

    Note: The above information is intended to supplement, not substitute for, the expertise and judgment of your physician, pharmacist, or other healthcare professional. It is not intended to diagnose a health condition, but it can be used as a guide to help you decide if you should seek professional treatment or to help you learn more about your condition once it has been diagnosed.

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