Facts about Pediculidae capitis,
better known as head lice

If you’ve found this website, your child likely has a case of head lice. We’ve compiled this information for your convenience; learn more on the FAQs page. The Nit Pickers staff is experienced and ready to assist your family in becoming lice-free. Contact us for more information or to schedule an appointment in our Northbrook or Schaumburg, Illinois, salons.

Head lice are members of the insect group Pthiraptera, family Pediculidae, which are obligate ectoparasites (parasites that live outside the body of the host). They belong to a particular subgroup of insects, known as sucking lice, because of their feeding mode. They live on the scalps and in the hair of humans.

Pediculidae have co-existed with humans since before recorded history, evolving from lice associated with our primate ancestors. Most experts consider the human head louse and human body louse variations of the same species: Pediculus humanus. Lice found on humans will not survive on other animal hosts; lice found on pets or other animals cannot survive on humans.

Physical Description
Wingless, they are about the same size as a sesame seed (1/32” to 3/16” long) with bodies that look somewhat flattened. A young adult louse is light gray; after ingesting blood its body may look dark red. Like chameleons, they blend in with their environment. They can move easily from hair to hair and their six pointed legs and specially adapted claws allow them to cling tightly to a hair shaft.

Females need to mate only once, then can begin laying viable eggs just 24 hours later. For the rest of her one-month life she may lay up to 300 eggs (three to five eggs twice daily). She securely glues each egg (commonly known as a nit”) to a single strand of hair.

Under normal conditions, eggs will hatch in eight to eleven days. There are three nymphal stages, lasting about seven to ten days. Between each stage, the louse molts in order to shed its exoskeleton or “skin.” During the final nymphal stage, body growth stops and sexual maturation occurs. An adult louse emerges at the third molt, hungry and ready to feed every four to six hours for the rest of its life.

Head lice eat nothing but human blood. A head louse penetrates scalp skin with its rasping teeth. Then it inserts its retractable proboscis into a blood vessel, injects a tiny amount of anticoagulants, and feeds much like a mosquito. Lice normally take several blood meals per day, resting between meals to digest its food.

Like mosquitoes, lice bites often are irritating and may lead to a cycle of itching and scratching. Disease transmission by head lice has not been proven; studies are ongoing. Psychological trauma, skin irritation at the feeding site and secondary bacterial infections introduced by scratching are all human health concerns associated with head lice.

Head lice can’t jump or fly but can crawl. Adults and nymphs cannot survive long without a human host, even under ideal conditions (low temperature and high humidity). Under normal conditions, lice will become dehydrated and unable to feed after 12 hours without a host. Eggs do not hatch at room temperatures; they need the warmth of a human body.

How do they spread? They find new human hosts about 98 percent of the time by direct hair-to-hair contact. Fewer than two percent of cases come from sharing combs, brushes, hats and other items. Occasionally lice might be transmitted from pillow cases or bedding.

Only adult or third stage nymphs transfer to a new host; eggs are cemented to hair and never leave a host. At least one fertilized female or one male and female must be present to begin an infestation or reinfestation.

Head lice signs, symptoms and diagnosis
Like a mosquito bite, a louse bite is painless. About half of those with lice are not allergic to the anticoagulant and therefore are asymptomatic. The other half develop an allergic reaction to the anticoagulant. Allergy symptoms are red marks, itching, swollen glands, low-grade fever, and sleepiness after a seemingly good night’s sleep; a person’s reaction varies. Someone without prior exposure to lice may have no symptoms for two weeks.

Scratching and breaking the skin creates an opening for lice feces and bacteria, possibly causing secondary infections and swollen glands in the neck. A low-grade fever and irritability (due to lack of sleep) cause an individual to feel “lousy.”

Finding a live louse or nit on the scalp or in the hair constitutes a definitive diagnosis. A person with head lice may itch, have red marks, scaling, rash and sores on the scalp.

Nits are sometimes confused with hairspray or hair gel residue or dandruff. These are easily removed from the hair while a nit is firmly attached. “Placebo nits” are also mistaken for nits. These are dried skin cells and hair follicle oil and are especially common in those who have already been treated with pediculicides.

Dermatitis, insect bites, eczema, psoriasis and fungal infections may mimic a lice infestation. Repeated treatment with pediculicides also often causes scalp irritation (scaling, rash and itching).

No eco-socio, racial, or ethnic group is exempt. Anyone with hair is susceptible to a head lice infestation; the groups most likely to get them are children and young teens. Some studies show that girls contact lice more often than boys.

Without removal of every nit and louse from one’s head, expect reinfestation.

Prescription Products
Lindane, banned in 52 countries, is in the class of chemical insecticides that includes DDT. Lindane is stored in human tissues and accumulates in the body with repeated use. Overusing, misusing or ingesting Lindane may cause central nervous system toxicity. Since Lindane has been available for more than 50 years, lice have built up resistance. Its use damages hair, creating a straw-like texture. Other options are safer and more effective.

Malathion has been marketed in the U.S. since 1999 as Ovide®. With a high isopropyl alcohol level and pine needle oil, this solution is smelly and flammable. Recommended usage includes leaving the product on the head for eight to twelve hours, making Malathion even less attractive a treatment.

Over the Counter Products
Derived from the flower heads of Chrysanthemum cinerariaefolium (pyrethrum) Pyrethrins, are used as an ingredient in lotions, shampoos, mousses and gels to treat head lice. Brand names include RID®, A-200®, Clear Lice System® and Pronto®; generic labels are also available. These products have low toxicity in mammals but persons with allergies to ragweed and flowers may also react to these products. Twenty to 80 percent of treated nits survive, necessitating a second treatment seven to ten days after the first application.

Permethrin, a synthetic modification of natural pyrethrins, is more heat and light stable, highly toxic to lice and less likely to trigger a toxic reaction in humans. Elimite®, Acticin®, Penederm®, and Nix® all contain this compound. Approximately 20 to 40 percent of treated nits survive a Nix treatment; studies suggest that lice have developed resistance to this drug.

Literally, nitpicking is the process of manually combing through and picking all nits from the hair. This manual nit removal is advised even after using a chemical product. Nit picking is a slow process that includes examining individual hairs from root to end and completely removing all nits with a special fine-toothed comb. Hair is usually parted and combed in sections; detangler or hair conditioner facilitates combing. Combs must be cleaned after each use.

Infested individuals should be checked for lice and nits every day for 14 days, repeating nitpicking as necessary until no more lice or nits are found. At this point, checking may take only 15 minutes daily.

Preventing transmission of head lice and eliminating their presence involves patience and time. Let The Nit Pickers help. Contact us for more information.

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