Head lice are tiny six-legged invertebrates that live on a person’s scalp. These lice lay tiny, oval-shaped eggs on hair shafts close to the scalp. The eggs of head lice are known as nits.

Head lice are parasites that feed on human blood. Their life cycle has three stages. It begins with an egg that hatches to release a nymph, and the nymph matures into an adult louse after three molts.

This article explores the differences between nits and lice and how to prevent them. It also answers some common questions about them.

Image of a child having their hair combed with a lice combShare on Pinterest
Richard Bailey/Getty Images

A head louse has three stages or forms across its life cycle: egg, nymph, and adult.

Nits are the eggs of head lice. Female lice firmly lay and glue them at the base of the hair shaft, about 6 millimeters (mm) from the scalp, to keep them warm. Any nits that appear further from the scalp may be empty shells, nonviable nits, or nits that have already hatched.

They are 0.8 to 0.3 mm in size, or about half the size of a pinhead, and are tear or oval-shaped.

Nits are yellow, tan, brown, or white but may appear the same as the color of the hair of its host. Once they hatch, nits become more visible and turn a dull yellow color, becoming difficult to see with the naked eye. Many people confuse nits for hairspray droplets, dandruff, or scabs.

Nymphs resemble adult louse but are smaller and are about the size of a pinhead. They grow larger every time they molt and mature after three molts.

Adult lice have six legs and are the size of a sesame seed. They are tan or grayish-white.

Nits are very small, do not move, and may be challenging to see with the naked eye. While lice are slightly bigger than nits, they crawl quickly and avoid light, so they may also be difficult to spot.

Head lice primarily transfer from one person to another through direct head-to-head contact. They may also spread when people share items such as combs or hair brushes. For example, nits attached to shed hair on a comb may hatch and spread when another person uses the comb.

Read more about how a person gets head lice.

Anybody can get lice, but children are more likely to get them because they tend to come in close contact with their peers when playing and sharing items.

A person can take the below precautions to help prevent lice from spreading:

  • Tell children to avoid head-to-head contact during play and other activities.
  • Do not share combs and brushes. Disinfect brushes and combs a person with lice may have used by soaking them in at least 130°F (54.5°C) water for 5–10 minutes.
  • Do not share clothing and other items such as scarves, hats, hair ties, headphones, and towels. Machine wash and dry clothing and other washable items someone with lice may have worn in the 2 days before they received lice treatment in hot water and a high heat drying cycle.
  • Dry-clean or seal and store nonwashable items a person with lice may have used in the 2 days before they received lice treatment in a plastic bag for 2 weeks.
  • Do not lie on beds, couches, pillows, or carpets where a person with lice has slept or sat. Vacuum carpets and upholstered furniture.
  • Do not use insecticide fogs or sprays to control lice. They can be harmful if someone inhales them or absorbs them into the skin.
  • Check everyone in the home several weeks after finishing lice treatment. Inform a healthcare professional if the treatment is ineffective and there are still live lice on someone’s scalp.

Learn more about effective ways to get rid of head lice.

Below are some of the most common questions about nits and lice.

Can someone have nits but no lice?

It may be possible to have nits but no lice. If a person cannot find any nymphs or adult lice in the scalp and the nits are more than a quarter of an inch from the scalp, these may be dead and from an old infestation.

However, the lice could be in hiding. Quick-moving lice tend to steer away from the light, which is why nits are more commonly visible than live nymphs or adult lice on a person’s scalp.

A person can speak with a healthcare professional for diagnosis and advice about lice treatment.

Learn more about the symptoms of head lice.

Do people get nits or lice first?

People get lice first. Nits are eggs that attach to hair shafts and cannot transfer or move from one head to another.

Generally, adult lice are more likely to transfer than nymphs. While first-generation nymphs are mobile, they are slower than fully grown lice and may need prolonged contact to transfer from one person’s head to another.

What kills nits?

Over-the-counter (OTC) lice treatment with Food and Drug Administration (FDA) approval kills lice but not nits. Malathion lotion, 0.5%, and spinosad, 0.9% topical suspension, are two FDA-approved lice treatments that may kill some nits.

A person can speak with a doctor for further information about lice treatment.

It is relatively easy to distinguish between nits and lice. Nits are small, oval-shaped eggs that firmly attach to a person’s hair and cannot move. Lice are tiny insects that hatch from and lay nits.

A person usually gets lice by having direct head-to-head contact or sharing personal items with someone who has lice. Nits cannot move or transfer from one individual to another.

OTC treatments may be effective for killing lice, but not nits. A person can consult with a healthcare professional about which lice treatment may be best for them and how to use it correctly.