Pediculus is the scientific name for lice, small parasitic insects living on humans. These wingless insects feed exclusively on human blood and spend their entire life cycle on a host. Lice infestations, known as pediculosis, are a widespread concern.
Types of Human Lice
Humans can be infested by three primary types of lice, each with distinct body habitats. Head lice, Pediculus humanus capitis, are the most frequently encountered, especially among children. These lice reside on the scalp and attach their eggs, called nits, firmly to hair shafts, often near the ears and nape of the neck.
Body lice, or Pediculus humanus humanus, are similar to head lice but larger. Unlike head lice, they live primarily in the seams of clothing and bedding, only moving to the skin to feed.
The third type, pubic lice (Pthirus pubis), often called “crabs,” are distinct, with a wider, crab-like body. They primarily infest pubic hair but can also be found in other coarse body hair like eyebrows, eyelashes, beards, and armpits.
Recognizing an Infestation
Symptoms often include intense itching on the scalp, body, or genital area. A tickling sensation from hair movement may also occur, and some individuals experience irritability or difficulty sleeping due to discomfort. Small red bumps or sores may develop from scratching on the scalp, neck, or shoulders, sometimes leading to bacterial infections. Visual inspection confirms an infestation.
When inspecting, focus on areas where lice and nits are commonly found: behind the ears and nape of the neck. Nits, or lice eggs, appear as tiny, oval, white or yellowish-brown objects, firmly glued to hair shafts within a quarter-inch of the scalp. Dandruff flakes, in contrast, are larger, irregular, and easily brushed off, as they are not attached to the hair shaft. Live adult lice are about the size of a sesame seed, gray or tan, and often move quickly, making them harder to spot than nits.
Effective Treatment Strategies
Treating a lice infestation involves several approaches, including over-the-counter (OTC) products, prescription medications, and non-chemical methods. OTC options contain active ingredients such as permethrin (e.g., Nix) or pyrethrins combined with piperonyl butoxide (e.g., RID). Permethrin is a synthetic pyrethroid that kills live lice, approved for use in individuals as young as two months. Pyrethrin-based products, derived from chrysanthemum flowers, paralyze and kill lice, but often require a second application 7-10 days later to eliminate newly hatched nymphs, as they may not kill all nits.
For persistent cases or when OTC treatments are ineffective, prescription medications are available. These include malathion lotion (Ovide), which kills both lice and some eggs, left on hair for 8-12 hours before rinsing. Spinosad (Natroba) lotion is another option, approved for individuals six months and older, requiring only one 10-minute application to kill lice and nits without nit combing. Ivermectin is available as a topical lotion (Sklice) for individuals six months and older, or as an oral tablet (Stromectol) for more resistant cases, given in two doses eight days apart.
Non-chemical removal, such as wet combing, is a safe and effective method for removing lice and nits. This involves applying ample conditioner to wet, detangled hair, which immobilizes lice, making them easier to comb out with a fine-toothed lice comb. Draw the comb from the scalp to hair ends, wiping it on a tissue after each stroke to remove lice or nits. Repeat this process every few days for at least 2-3 weeks to ensure all newly hatched lice are removed before laying new eggs.
Alongside treating the individual, cleaning personal items is recommended. Machine-wash clothing, bedding, and towels in hot water (at least 130°F/54°C) and dry on high heat for at least 20 minutes to kill stray lice or nits. Non-washable items can be sealed in a plastic bag for two weeks to ensure remaining lice die from lack of a host. Vacuuming carpets and upholstered furniture can also help remove lice that may have fallen off.
Prevention and Control
Preventing future lice infestations involves minimizing transmission opportunities. Avoiding head-to-head contact, especially among children during play, sports, or sleepovers, is a primary preventive measure. Lice do not jump or fly; they spread via direct crawling contact.
Discourage the sharing of personal items that contact the head, such as combs, brushes, hats, scarves, coats, and headphones. Combs and brushes used by an infested person should be disinfected by soaking in hot water (at least 130°F/54°C) for 5-10 minutes.
Regular checks for lice during known outbreaks in schools or daycare centers can aid in early detection and prompt treatment, limiting further spread. Informing schools or other parents about a discovered infestation benefits broader community control efforts.