All types of lice share two things in common: They spread via human contact, and they feed on blood.

Lice are types of parasitic insects that feed on human blood. There are three types:

  • head lice (Pediculus humanus capitis)
  • body lice (Pediculus humanus corporis)
  • pubic lice, or “crabs” (Pthirus pubis)

Read on to learn about how lice survive and spread, as well as your treatment options for getting rid of them.

Whether you have lice on your head, pubic area, or elsewhere, all of these parasites survive by sucking on blood. They do this by biting your skin to retrieve blood for feeding.

Without human blood, lice become dehydrated and can’t survive or lay their eggs (called “nits”). Most head lice can’t survive without blood longer than 1 to 2 days. Body lice may live without human blood for 2 to 5 days.

Nits are lice eggs that lay along skin folds, in your hair, or in the seams of clothing. Nits don’t suck blood like lice do because they’re unhatched eggs.

Once nits hatch, they’re known as “nymphs” until they mature into adults after several days. Like adult lice, nymphs need human blood to survive.

Lice drink human blood several times per day. The amount of blood you lose depends on the number of lice you have, as well as how long you’ve been experiencing the infestation. While uncommon, there have been reports of acute anemia due to large blood losses from lice.

When lice drink blood, their body masses increase rapidly. According to a 2022 study, female lice grew about 52% larger after feeding on blood. However, the lice were also found to decrease rapidly in size within 60 minutes after feeding.

In order to feed on human blood, lice create small bites on your skin. This results in the notorious itching associated with lice infestations.

Lice can also leave itchy bumps in their wake. Depending on your natural skin color, these can look like small red to purple papules or cysts.

Lice don’t suck on the blood of pets, so your dog or cat can’t get these types of infestations. Also, lice can’t be transmitted between pets and people.

Instead, if you have a dog, cat, or other pet who may be itchy or has visible bugs in their skin or fur, you may consider talking with a vet about fleas, mites, or ticks. These are all types of parasites that can affect pets.

Lice can’t jump or fly. Instead, they simply crawl.

Since lice are spread between people, the parasites crawl from one person to another upon contact. It’s also possible to get lice if any of the parasites or their nits live on clothing, bedding, or furniture. Sharing items, such as hairbrushes or towels, can also increase your risk of getting lice.

Lice are spread easily via human contact, particularly in crowded spaces. While anyone can get lice, head lice are the most common, and they primarily spread among schoolchildren as well as their parents and caregivers.

Body lice also tend to be more common in conditions where one may not have access to regular hygienic practices or laundering. These types of lice also like to hide in the creases of fabric, such as clothes and bedding.

Pubic lice are most often spread by sexual contact. However, these types of lice may also sometimes reside in other parts of the body with coarse hair, such as beards, armpits, or eyebrows.

While not considered life threatening, having an untreated head lice infestation can pose other risks, such as:

  • extreme itchiness throughout the day
  • itchiness that can keep you up at night
  • sores on your scalp from scratching, which may bleed or become infected
  • missed days of school and work in your household

The risks associated with lice depend on the type you have. Head lice aren’t considered fatal, nor do they transmit diseases.

According to one 2023 narrative review on lice in Africa, researchers noted that body and pubic lice might spread bacterial infections, such as typhus. However, typhus from body lice is now considered rare in the United States.

Also, while not common, it’s possible to experience acute anemia from blood losses associated with lice.

Depending on the severity of the infestation, a doctor may recommend either an over-the-counter or prescription lice treatment.

Other treatment options include:

  • wet-combing for head lice
  • washing all clothing, bedding, and towels at 130°F (54°C) or higher if you or someone in your household has lice
  • vacuuming carpets, upholstery, and mattresses
  • sealing unwashable items, such as stuffed animals, in a plastic bag for 1 month

Whether you have head, body, or pubic lice, all of these types of parasites need human blood to survive. They do this by biting your skin and sucking blood several times a day. This can cause irritation and itchiness.

Lice are rarely deadly, but they can sometimes lead to secondary infections. It’s important to speak with a doctor about treatment options if you or your child has a suspected lice infestation.