How Long Do Lice Live Without a Host?

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There are many urban myths surrounding head lice, including that you can catch head lice from your bedding or even from your pets.

In this article, we’ll debunk some of those common misconceptions about head lice. And we’ll answer the often-asked question, “How long do lice live without a host?”

What are head lice?

Head lice

Head lice are parasitic insects that live on the head of a human host, feeding on the victim’s blood.

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Head lice are highly contagious, moving from one person to another through direct head-to-head contact. School children are most commonly affected with an estimated six to 12 million kids aged between three and 11 years contracting head lice every year.

Lice live close to the scalp where it’s warm and humid, sometimes infesting the eyebrows and eyelashes too. Common symptoms of head lice include an itching, tickling feeling on your scalp, and visible signs such as tiny white specks (lice eggs) in your hair.

Lice need human blood to survive; they can’t feed on animals or birds.

The louse life cycle

Unlike bed bugs, lice must live on their host. Lice move around by crawling and climbing up the hair shaft; they can’t jump, fly, or swim. Lice are perfectly adapted to life on the human head, using their six claws to cling to the hair shaft and move around their environment.

Lice begin life as tiny, whitish-yellow eggs, commonly called “nits.” The female louse lays her eggs on the host’s hair shaft, attaching the nits with a sticky, glue-like substance. Once attached, the nits are extremely difficult to remove, and the empty shells remain stuck to the hair even after the juvenile louse (nymph) has hatched and moved on.

Nits take between seven and ten days to hatch. Once the nymphs have hatched, they begin feeding on the host’s blood. After nine to 12 days, nymphs are fully mature and can start to breed.

Adult head lice can live on their host’s blood for three to four weeks. During this time, female lice lay eggs up to six times each day before they die, so you can see how rapidly a full-scale infestation can take hold.

How long do lice live without a host?

Sometimes, lice or nits may become dislodged onto inanimate objects such as a pillowcase, comb, or hat. In theory, it’s possible that lice can pass to another host through the immediate sharing of these objects. However, adult lice cannot survive for more than 30 hours without the warmth and food that they get from their human host.

So, any lice or nits that end up on your carpets or furniture will die long before they are likely to end up in your hair. Similarly, nits need the warmth and humidity of the human scalp for incubation and to mature and hatch.

As soon as they emerge from the nits, nymphs need the nourishment that they can only derive from human blood. Any nits that are dislodged from the hair will usually die before they get a chance to hatch.

If you have a dog or a cat, don’t worry; lice can only survive on human blood. Lice or nits that end up on your pets will die within 30 hours.

Although lice can survive for up to eight hours in water, they’ll quickly die because they’re separated from their food source. Lice are unable to swim, so they can’t paddle their way across your local swimming pool to a new host!

Preventative measures to kill lice and nits

So, you can see that the only way lice can move from one person to another is by direct head-to-head contact. They can’t survive away from a human host for more than 30 hours.

However, to put your mind at rest, there are a few steps you can take to prevent any dislodged lice and nits from finding their way onto a human head:

  • Wash all your bed linen, clothing, and towels in water that is at least 130°F. Then, put everything in your tumble dryer on the hot cycle for at least 20 minutes.
  • Items that are not washable should be placed in large plastic bags. Seal the bags for at least 72 hours to kill any lice, nymphs, and nits that are trapped inside.
  • Vacuum all your carpets and furniture, and then dispose of the vacuum cleaner bag by burning it.
  • Take all hair-care items such as combs, hairbrushes, scrunchies, barrettes, and headbands, and soak them in a medicated shampoo or in rubbing alcohol for at least one hour. Rinse thoroughly in very hot water, ideally in a dishwasher.

Wrapping it up

So, the bottom line …

  • Head lice and nits cannot survive away from a human host for more than 30 hours.
  • Head lice and nits cannot live on pets, carpets, upholstery, or inanimate objects.
  • Theoretically, head lice and nits could survive for a short time in hairbrushes, combs, hats, etc. To be on the safe side, soak all these items in medicated shampoo or in rubbing alcohol for at least one hour. Rinse thoroughly in very hot water.

To prevent the accidental transfer of lice, do not allow children to share hair accessories, hats, etc., and prevent head-to-head contact if possible.

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