Frequently Asked Questions About Head Lice

Answers adapted from content on the websites of the National Pediculosis Association (NPA) & Harvard School of Public Health (HSPH)

Head lice do not come "out of the air" or from the ground. They are human parasites and have probably been here since the beginning of time. Desiccated (dried up) head lice and their eggs have been found on the hair and scalps of Egyptian mummies. Lots of folks have misconceptions about head lice and the people who have them. Head lice can affect anyone: rich or poor, young or old, male or female. An outbreak of head lice in your family does not mean that you're a bad housekeeper or that you don't bathe. It does mean loss of school for kids, loss of work time for parents, and often the unnecessary use and misuse of potentially harmful pesticide treatments

Head lice rarely (if ever) cause direct harm, and they are not known to transmit infectious agents. Thus, they should not be considered as a medical or a public health problem. These lice may occasionally be burdensome because of annoyance; their presence may cause itching and loss of sleep. The greatest harm associated with head lice results from the well-intentioned but misguided use of caustic or toxic substances to eliminate the lice.

The sooner nits (louse eggs) and head lice are detected, the easier and quicker it is to control and remove them.... because they multiply quickly. This is the reason why the National Pediculosis Association® (NPA) recommends that parents screen their children regularly (several times a week) as part of routine hygiene.

Head lice can survive on a human host for approximately 30 days. Head lice generally cannot survive longer than 24 hours off the host. A female louse lays up to 3-5 eggs per day. It takes 7-10 days for the eggs to hatch and another 7-10 days for the louse to mature and lay their own eggs.

Head lice can be spread whenever there is direct contact of the head or hair with an infested individual. Lice can also be spread through the sharing of personal articles like hats, towels, brushes, helmets, hair ties and so on. There is also a possibility that head lice can be spread via a pillow, head rest, or similar item. Head lice do not jump or fly and generally cannot survive longer than 24 hours off the host.

Head lice do not leave a head in search of new hosts. If a louse comes off the head and is left behind (i.e. on a pillow or a head rest) it may be possible for the louse to infest another individual who places their head in that area. Vacuuming is recommended for any areas or items that may be in regular contact with those who may be infested.

Swimming with someone who has lice carries no greater risk of transmission than any other activity, nor will the water affect the infestation. When lice are in water they go into a state of suspended animation but remain firmly locked onto the hair – literally hanging on for dear life. Lice or nits that might detach in a swimming pool would likely be removed by the pool filter or otherwise perish before contacting another person. Closing a swimming pool because of lice is not indicated. Risks of transmission will occur, however, with the sharing and piling of towels, storing other personal items and clothing in close proximity, and direct head to head contact.

Head lice cannot thrive on pets… they are human parasites. The extent to which head lice are transmitted to others via headphones and helmets is unknown, but considered rare. Still, risks of transmission are minimized when children have and use their own equipment. When sharing is necessary, the items can be cleaned between kids by wiping them with a damp paper towel. Children can also wear a baseball cap to help shield the hair from contact with the items. Helmets and headphones should never be sprayed! Most importantly – and best for the entire community – all parents should regularly screen their children for head lice and nits (at least twice weekly).

Homes don’t get head lice – people do. Head lice are human parasites and require human blood to survive. Please do not use any pesticidal sprays in your home. They are unwarranted and may pose personal and environmental hazards. Vacuuming is the safest and best way to remove lice or fallen hairs with attached nits from upholstered furniture, rugs, stuffed animals and cars. It is unnecessary to bag objects that can be washed and dried (see below). Vacuum them instead. Save your time and energy for that which benefits you the most – thorough nit removal.

Treatment should be considered only when active lice or viable eggs are observed. There are no safe pesticides, "natural" or otherwise, scientifically proven to be 100% effective against head lice, nits or nit glue. Reliance on head lice treatment products alone promotes repeated use of potentially harmful chemicals and contributes to ongoing infestations, outbreaks, and resistant strains of lice. Parents are discouraged from spending unnecessary time and money on "concoctions" for which there is no scientific basis for claims or evidence of efficacy and human safety. A wide variety of "lice remedies" are vigorously marketed to consumers especially via the Internet, and can have harmful effects. The result is more confusion for families already deluged with conflicting and unfounded treatment recommendations. Manual removal is the safe alternative to, and a necessary component of, any head lice treatment regimen. The NPA recommends a combing tool (the LiceMeister®[1]) to enable families to screen often, detect head lice early, and thoroughly remove lice and nits.[2] Removal of live lice and nits by combing is assisted when the hair is first moistened with a hair conditioner or salad oil (e.g., canola, corn).

Parents should be informed about the potential risks before they shampoo with any product. This is just one of the reasons the FDA requires testing for safety before they give their approval. Safety varies from person to person just as the status of one's health varies. Children who have had earlier repeated lice treatments may also be more vulnerable to side effects. The NPA warns against the use of any chemicals designed to kill or destroy head lice in individuals who have pre-existing illness, such as epilepsy, asthma, brain tumors, cancer or AIDS, and for pregnant or nursing women. Those on medication should also be aware that there can be unspecified chemical interactions.

Experts used to suggest bagging items, such as stuffed animals, for a number of weeks to help bring infestations under control. To our knowledge there is no evidence that this measure is helpful in any way because head lice require human blood to survive. What we do know is that parents and others spend invaluable amounts of time with "bagging" at the expense of more beneficial "hands-on" screening and nit removal. Save your physical and emotional energies for screening and thorough lice and nit removal. Vacuuming is a sufficient safeguard for any questionable areas or items that may be in regular contact with those who may be infested. You can also take bed linens and other items and put them in a hot dryer for 30 minutes. Remember -- NEVER EVER SPRAY.

The NPA does not get into "dead or alive" – the time it would take to make the distinction is time better spent by removing ALL nits. Children, like adults, do not want them left in their hair – dead or alive. (The Harvard School of Public Health experts do make the distinction since dead nits cannot cause reinfestation.)

Nits are visible to the naked eye in natural light. If you are unsure whether you are seeing a nit, or to determine if a nit is viable, a magnifying glass and training may be needed, or for even better results…use the LiceMeister® combing tool to screen through the hair. It will collect even that which you cannot see. Too often nits are confused with hair debris, and children are being treated unnecessarily. Make sure that screeners know the difference!

[1] LiceMeister® is a metal comb developed by the NPA. Metal combs are considered more effective than plastic ones; other metal combs may also be effective.

[2] Current medical recommendations include complete nit/louse removal, or one use of an over-the-counter product (giving 2 doses if directed). If those fail, consult your physician regarding one use of a prescription product.

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