Head lice infestation
|Head lice infestation (pediculosis capitis)|
Head lice bites on the back of the neck
|Classification and external resources|
Head lice infestation (also known as pediculosis capitis, nits, or cooties) is the infection of the head hair and scalp by the head louse (Pediculus humanus capitis). Itching from lice bites is common. During a person's first infection, the itch may not develop for up to six weeks. If a person is infected again, symptoms may begin much more quickly. The itch may cause problems with sleeping. Generally, however, it is not a serious condition. While head lice appear to spread some other diseases in Africa, they do not appear to do so in Europe or North America.
Head lice are spread by direct contact with the hair of someone who is infected. The cause of head lice infestations are not related to cleanliness. Other animals, such as cats and dogs, do not play a role in transmission. Head lice feed only on human blood and are only able to survive on human head hair. When adults, they are about 2 to 3 mm long. When not attached to a human, they are unable to live beyond three days. Humans can also become infected with two other lice – the body louse and the crab louse. To make the diagnosis, live lice must be found. Using a comb can help with detection. Empty eggshells (known as nits) are not sufficient for the diagnosis.
Possible treatments include: combing the hair frequently with a fine tooth comb or shaving the head completely. A number of topical medications are also effective, including malathion, invermectin, and dimeticone. Dimeticone, which is a silicone oil, is often preferred due to the low risk of side effects. Pyrethroids such as permethrin have been commonly used; however, have become less effective due to increasing resistance. This is little evidence for alternative medicines.
Head-lice infestations are common, especially in children. In Europe, they infect between 1 and 20% of different groups of people. In the United States, between 6 to 12 million children are infected a year. They occur more often in girls than boys. It has been suggested that historically, head lice infection were beneficial, as they protected against the more dangerous body louse. Infestations may cause stigmatization of the infected individual.
Signs and symptoms
Head lice are generally uncomfortable, but typically do not constitute a serious condition. The most common symptom is itching of the head, which normally worsens 3 to 4 weeks after the initial infestation. The bite reaction is very mild, and it can be rarely seen between the hairs. Bites can be seen, especially in the neck of long-haired individuals when the hair is pushed aside. Swelling of the local lymph nodes and fever are rare. Itching may cause skin breakdown and uncommonly result in a bacteria infection.
Head lice are generally spread through direct head-to-head contact with an infested person. Transmission by sharing bedding or clothing such as headwear is much less common. The cause of head lice infestations are not related to cleanliness.
Body lice are spread through direct contact with the body, clothing, or other personal items of a person already carrying lice. Pubic lice are most often spread by intimate contact with an infested person. Head lice occur on the head hair, body lice on the clothing, and pubic lice mainly on the hair near the groin. Lice cannot burrow into the skin.
The condition is diagnosed by finding live lice in the hair. Finding empty eggs is not enough. This is made easier by using a magnifying glass or running a comb through the child's hair. In questionable cases, a child can be referred to a health professional. However, the condition is overdiagnosed, with extinct infestations being mistaken for active ones. As a result, lice-killing treatments are more often used on noninfested than infested children. The use of a louse comb is the most effective way to detect living lice. With both methods, special attention should be paid to the area near the ears and the nape of the neck. The use of a magnifying glass to examine the material collected between the teeth of the comb could prevent misdiagnosis.
The presence of nits alone, however, is not an accurate indicator of an active head louse infestation. Generally, white nits are empty egg casings, while brown nits may still contain viable louse larva. One way of determining the nit is to squeeze it between two fingernails; it gives a characteristic snapping pop sound as the egg bursts. Children with nits on their hair have a 35–40% chance of also being infested with living lice and eggs. If lice are detected, the entire family needs to be checked (especially children up to the age of 13 years) with a louse comb, and only those who are infested with living lice should be treated. As long as no living lice are detected, the child should be considered negative for head louse infestation. Accordingly, a child should be treated with a pediculicide only when living lice are detected on their hair (not because he/she has louse eggs/nits on the hair and not because the scalp is itchy).
Examination of the child's head at regular intervals using a louse comb allows the diagnosis of louse infestation at an early stage. Early diagnosis makes treatment easier and reduces the possibility of infesting others. In times and areas when louse infestations are common, weekly examinations of children, especially those 4–15 years old, carried out by their parents, will aid control. Additional examinations are necessary if the child came in contact with infested individuals, if the child frequently scratches his/her head, or if nits suddenly appear on the child's hair. Keeping long hair tidy could be helpful in the prevention of infestations with head lice.
Clothes, towels, bedding, combs, and brushes, which came in contact with the infested individual, can be disinfected either by leaving them outside for at least two weeks or by washing them at 60 °C (140 degrees F) for 30 minutes. This is because adult lice can survive only one to two days without a blood meal and are highly dependent on human body warmth. An insecticidal treatment of the house and furniture is not necessary.
Shaving the head can effectively treat lice. Wet combing a few times a day for a few weeks may also get rid of the infestation in half of people. This requires the use of a special lice comb with extra fine teeth. This is the recommended method for infants and women who are pregnant.
There are many medications which can kill lice. Dimeticone is between 70 and 97% effective with a low rate of side effects, and thus is seen as the preferred treatment. It works by physical means and there is no evidence of resistance. Invermectin is around 80% effective, but can cause local skin irritation. Malathion has an effectiveness around 90%, but there's the possibility of toxicity. Pyrethroids such as permethrin, while commonly used, have lower rates of effectiveness due to the resistance among lice. Effectiveness varies from 10 to 80%, depending on the population studied. Medications within a lotions appear to work better than those within a shampoo.
Tea tree oil has been promoted as a treatment for head lice; however, there is disagreement on its effectiveness. A 2012 review of head lice treatment recommended against the use of tea tree oil for children because it could cause skin irritation or allergic reactions, because of contraindications, and because of a lack of knowledge about the oil's safety and effectiveness. Other home remedies, such as putting vinegar, isopropyl alcohol, olive oil, mayonnaise, or melted butter under a shower cap, have been disproven. The CDC states that swimming has no effect on lice, and can decrease the effectiveness of some treatments.
After treatment, people are often instructed to wash all bedding and vacuum all areas the head may have been, such as car seats, coat hoods, and sofas, but this is not always necessary, since adult lice will die within 2 days without a blood meal, and newly hatched lice die within minutes of hatching. Combs and brushes may be deloused in boiling water for 5–10 minutes. Items may also be frozen for 24 hours well below the freezing point of water to ensure that ice crystals form within the cells of the lice.
|“||Reliable data describing the usual incidence of infestation in the general public, in the average school community, or during specific times of the year are lacking.||”|
—Janis Hootman, 2002
The number of cases of human louse infestations (or pediculosis) has increased worldwide since the mid-1960s, reaching hundreds of millions annually. It is estimated between 1 to 20% of specific groups in Europe are infected.
Despite improvements in medical treatment and prevention of human diseases during the 20th century, head louse infestation remains stubbornly prevalent. In 1997, 80% of American elementary schools reported at least one outbreak of lice. Lice infestation during that same period was more prevalent than chickenpox.
About 6–12 million children between the ages of 3 and 11 are treated annually for head lice in the United States alone. High levels of louse infestations have also been reported from all over the world, including Israel, Denmark, Sweden, U.K., France, and Australia.
The number of children per family, the sharing of beds and closets, hair washing habits, local customs and social contacts, healthcare in a particular area (e.g. school), and socioeconomic status were found to be significant factors in head louse infestation. Girls are 2–4 times more frequently infested than boys. Children between 4 and 13 years of age are the most frequently infested group. In the U.S., African-American children have lower rates of infestation.
The United Kingdom's National Health Service and many American health agencies  report that lice "prefer" clean hair because it's easier to attach eggs and to cling to the strands; however, this is often contested.
Head lice (Pediculus humanus capitis) infestation is most frequent on children aged 3–10 and their families. Females get head lice twice as often as males, and infestation in persons of Afro-Caribbean or other black descent is rare because of hair consistency. But these children may have nits that hatch and the live lice could be transferred by head contact to other children.
- To a Louse (on a lady's bonnet). Perhaps the most widely known cultural reference to pediculosis capitis, occurring in a noted poem by Robert Burns.
- Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 1-4160-2999-0.
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- "Parasites - Lice - Head Lice Frequently Asked Questions (FAQs)". cdc.gov. September 24, 2013. Retrieved 23 October 2014.
- "Head lice. Dimeticone is the pediculicide of choice.". Prescrire Int. 151 (23): 187–90. Jul 2014. PMID 25162097.
- "Parasites - Lice - Head Lice". cdc.gov. September 24, 2013. Retrieved 23 October 2014.
- Takano-Lee M, Edman JD, Mullens BA, Clark JM (December 2004). "Home remedies to control head lice: assessment of home remedies to control the human head louse, Pediculus humanus capitis (Anoplura: Pediculidae)". Journal of Pediatric Nursing 19 (6): 393–8. doi:10.1016/j.pedn.2004.11.002. PMID 15637580.
- Rózsa, L; Apari, P (May 2012). "Why infest the loved ones--inherent human behaviour indicates former mutualism with head lice.". Parasitology 139 (6): 696–700. doi:10.1017/S0031182012000017. PMID 22309598.
- Division of Parasitic Diseases (DPD), National Center for Zoonotic, Vector-Borne, and Enteric Diseases (ZVED) (May 16, 2008). "Head lice fact sheet". Centers for Disease Control and Prevention website. Atlanta, GA: Department of Health and Human Services, US Government. Retrieved 28 May 2010.
- Pollack RJ, Kiszewski AE, Spielman A; Kiszewski; Spielman (2000). "Overdiagnosis and consequent mismanagement of head louse infestations in North America". The Pediatric Infectious Diseases Journal 19 (8): 689–93. doi:10.1097/00006454-200008000-00003. PMID 10959734.
- Mumcuoglu KY, Friger M, Ioffe-Uspensky I, Ben-Ishai F, Miller J; Friger; Ioffe-Uspensky; Ben-Ishai; Miller (2001). "Louse comb versus direct visual examination for the diagnosis of head louse infestations". Pediatric dermatology 18 (1): 9–12. doi:10.1046/j.1525-1470.2001.018001009.x. PMID 11207962.
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- Mumcuoglu, Kosta Y.; Barker CS; Burgess IF; Combescot-Lang C; Dagleish RC; Larsen KS; Miller J; Roberts RJ; Taylan-Ozkan A. (2007). "International Guidelines for Effective Control of Head Louse Infestations". Journal of Drugs in Dermatology 6 (4): 409–14. PMID 17668538.
- Kidshealth.org – Head lice, page-3
- University of Florida Dept of Entomology Circular 175
- Goates BM, BM et al. (5 November 2006). "An Effective Nonchemical Treatment for Head Lice: A Lot of Hot Air". Pediatrics (American Academy of Pediatrics) 118 (5): 1962–1970. doi:10.1542/peds.2005-1847. PMID 17079567. Retrieved 2010-08-02.
- Barker SC, Altman PM (2010). "A randomised, assessor blind, parallel group comparative efficacy trial of three products for the treatment of head lice in children--melaleuca oil and lavender oil, pyrethrins and piperonyl butoxide, and a 'suffocation' product". BMC Dermatology 10: 6. doi:10.1186/1471-5945-10-6. PMC 2933647. PMID 20727129.
- Jacobi, Tillmann (22 September 2011). "The Basics – The management of head lice". GP: 38.
All in all, the evidence for alternative treatments, such as tea tree oil and neem seed oil, remains weak.
- "Tea tree oil". Medline Plus, a service of the U.S. National Library of Medicine from the National Institutes of Health. 27 July 2012.
- Eisenhower, Christine; Farrington, Elizabeth Anne (2012). "Advancements in the Treatment of Head Lice in Pediatrics". Journal of Pediatric Health Care 26 (6): 451–61; quiz 462–4. doi:10.1016/j.pedhc.2012.05.004. PMID 23099312.
- "CDC – Frequently Asked Questions – Healthy Swimming & Recreational Water – Healthy Water". Cdc.gov. 2012-10-22. Retrieved 2012-11-22.
- Michigan Head Lice Manual. State of Michigan. 2004.[page needed]
- Hootman J (April 2002). "Quality improvement projects related to pediculosis management". The Journal of school nursing : the official publication of the National Association of School Nurses 18 (2): 80–6. doi:10.1177/10598405020180020401. PMID 12017250.
- Norman G. Gratz (1998). "Human lice: Their prevalence, control and resistance to insecticides. A review 1985–1997" (PDF). Geneva, Switzerland: World Health Organization. Retrieved 2008-01-02.
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- Ian Burgess (2004). "Human Lice and their Control". Annual Review of Entomology (Annual Reviews) 49: 457–481. doi:10.1146/annurev.ento.49.061802.123253. PMID 14651472.
- Mumcuoglu KY, Miller J, Gofin R et al. (September 1990). "Epidemiological studies on head lice infestation in Israel. I. Parasitological examination of children". International Journal of Dermatology 29 (7): 502–6. doi:10.1111/j.1365-4362.1990.tb04845.x. PMID 2228380.
- Nutanson I. et al. (2008). "Pediculus humanus capitis: an update". Acta Dermatoven 17 (4): 147–59.
- James GH Dinulos (September 2008). "Lice (Pediculosis)". The Merck Manual. Merck & Co., Inc. Retrieved 2008-12-27.
- "Lice (Pediculosis)". The Merck Veterinary Manual. Whitehouse Station, NJ USA: Merck & Co. 2008. Retrieved 2008-10-08.