Medical Conditions - Lice

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(Head Lice, Pediculosis)

The Facts

Lice are tiny parasitic insects that can take up residence in a number of different places on our body. They are not a serious medical problem, but they can be annoying and can easily spread and infect others. Lice have been around for centuries. They were widespread in Europe up until the last century, and anthropologists report signs of these annoying intruders among Egyptian mummies and during the period of the ancient Greeks.

Life for a louse begins as a nit (egg). Nits are commonly found glued to the base of the hair shaft, frequently behind the ears or on the nape of the neck. It takes about 5 to 10 days for nits to hatch and for the light-coloured nymphs to begin feeding immediately. It takes about 7 or more days for the nymphs to mature.

Head lice (Pediculus humanus capitis) are found in the hair on the head. They are often spread among school children by close contact, clothing, or hairbrushes. They most commonly infect girls aged 5 to 11 years old, but since they spread easily, they can infect anyone. Head lice can infest clothing and other items that come in contact with the head (e.g., hats, shirt collars, brushes, combs, etc.). Unfed adult lice may survive up to 3 days away from the host. In general, the eggs hatch within a week and adult head lice have a lifespan of 1 to 2 days away from the host.

Body lice (Pediculus humanus corporis) are found on various parts of the body and are passed on through shared clothing or bedding. Unlike head lice, body lice attach their eggs to clothes fibres, particularly along inside seams and other areas of close body contact. A female body louse usually deposits 9 to 10 eggs per day, and a total of 270 to 300 eggs over her lifetime. The eggs are incubated by the person’s body heat and hatch in about one week. Development time (egg to adult) takes about 3 to 5 weeks. Body lice may carry serious diseases such as epidemic typhus and trench fever.

Pubic lice (Phthirus pubis), commonly referred to as crabs, live on the skin and hair of the pubic area and are spread by sexual contact, shared clothing, and bedding. Pubic lice can also attach themselves to the eyelashes.

Head lice are found in most urban schools, where a few cases are reported every year, usually early in the fall when children return to school. Contrary to popular opinion, head lice can infect clean heads as often as dirty ones. They are more common in girls than in boys, although not necessarily more common in girls with long hair. Head lice do not carry disease.

Human lice are not transmitted from dogs, cats, or other pets.


Head lice are usually spread among children crowded together in urban daycare centres and primary schools. They have no wings, so they cannot jump or fly from person to person; they move by crawling quickly or by grasping a shaft of hair with tiny front claws and then swing from one hair strand to another. In this way, they travel by direct head to head contact when children play with their heads close together or indirectly through sharing hats, coat hooks, scarves, bike helmets, headphones, hairbrushes, toys, or bedding. Poor hygiene does not play a role in head lice, although it does in body lice.

Body lice are usually found among people in cramped, crowded conditions and mainly affect those living in military barracks, as well as poor and homeless people. They are generally rare today thanks to improved sanitation, frequent bathing, and changing of clothes.

Pubic lice are transmitted by sexual contact, mainly among adolescents and young adults, but also can be transmitted by sharing towels and through sheets and clothing.

Symptoms and Complications

The primary symptoms include:

  • evidence of lice on the scalp, body, clothing, or pubic or other body hair
  • intense itching
  • nits on hair shafts
  • small, red lesion at each new feeding site

A person may not experience any initial symptoms of head lice – the itching may not start until a week or two after the initial infestation. Some people never feel itchy at all.

Scratching is the cause of most complications due to lice, as it can cause abrasions that may lead to secondary infections. Some people with lice develop hives, scalp scabs, and enlarged neck nodes.

Making the Diagnosis

Head lice or nits are the easiest to see, usually on the scalp and nape of the neck and over the ears. Adult lice are approximately the same size as a sesame seed. Body lice are more difficult to find, but they usually can be detected in the seams of underwear. Pubic lice are found on the skin and hair of the pubic area or on the eyelashes.

Finding a louse or nit is not easy. They are barely visible to the naked eye, especially on blonde hair, where they hardly show up at all. When looking for head lice, check behind the ears, close to the scalp at the back of the neck, and on top of the head. Using a fine tooth louse comb is far more efficient than simple visual examination. Be on the lookout for their tiny white glistening eggs or little gray hatched ones, which will be firmly attached to the hair shaft, usually close to the scalp. Lice excrement looks like flecks of brown dust.

Treatment and Prevention

Medication for lice includes lotions, cream rinses, and shampoos. For head lice, both pesticide and non-pesticide products are available. Apply the medication to the affected body areas as directed. Some people find that the effectiveness will vary with the type of product and thoroughness of application. Repeated treatments may be needed and are usually recommended. Ask a pharmacist for complete directions on how to use specific products and for recommendations on treatments based on the age of the affected person and the type of infestation. Note that this step gets rid of the existing adult lice.

Removing the remaining nits with tweezers or a fine comb is the next task in getting rid of lice. This can take several hours per head depending on the length of the hair and the number of nits. In the past, some schools had "no-nit" policies for children returning to class. Now, these policies are considered outdated and unnecessary.

All lice treatments should also be used on other affected family members (head lice) and sexual partners (pubic and body lice) at the same time as the infected person. Then, everyone treated must recheck once a week for a few weeks to ensure that there are no signs of lingering lice.

Alternative treatments to remove and kill lice, including "natural" treatments such as tea tree oil and aromatherapy; or "home remedies" such as mayonnaise, petroleum jelly, olive oil, and tub margarine are not currently recommended because there is not enough scientific evidence that they are effective.

Here are some anti-lice strategies:

  • Teach children not to share hats, headphones, combs, brushes, or bicycle helmets, and to report any head itching.
  • Keep long hair tied back and away from the face.
  • Check children’s hair regularly, especially if they are scratching a lot.
  • Wash all personal items that have come in contact with the head of an infested person at the time of a lice outbreak, such as hats, towels, and pillowcases, in hot water (above 55°C or 130°F) and dry in a hot dryer for at least 15 minutes.
  • Because lice can’t survive away from humans, non-washable things such as pillows can be dry-cleaned or sealed in airtight plastic bags for 14 days to kill lice.
  • Don’t use a pesticide spray to "disinfect" your house. These products can be toxic, and don’t help control head lice.
  • Soak all brushes and combs in hot water for 5 to 10 minutes or wash them with a pediculicidal shampoo.
  • Thoroughly vacuum items such as rugs, furniture, mattresses, pillows, and any other surface where someone may have rested their head. Do not forget the car seats.

Many parents are reluctant to report their children’s lice to school officials due to embarrassment, but it’s extremely important to do so to help control its spread. If head lice are noticed, also alert other people who may have had contact with your child.

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