How Do Lice Look – Growth, Morphology, and Treatment

Albeit annoying and sometimes hard to get rid of, lice are completely harmless. No need to worry or feel embarrassed if you or your children contract them. That said, they are highly contagious and spread fast unless treated in time. This is one of the reasons lice epidemics happen at nurseries, schools, and daycares.

How do lice look and are you likely to contract them?

Unfortunately, there are up to 12 million lice infestation cases every year in the US alone. Women and girls tend to be more susceptible to them, but this doesn’t mean men or boys are immune.

Recognizing them isn’t too difficult. The following sections should help you understand how to spot lice and treat them as well.

What Are Lice?

Pediculus humanus capitis, or the head louse, is an ectoparasite that thrives on the human head/hair. An adult louse has six legs which allow it to easily attach to the human head. The legs are also stumpy and short, which is why a louse cannot walk on flat surfaces or jump. This parasite doesn’t have wings.

Head lice affect only humans. Other kinds of lice, like Pediculus schaeffi, infect chimpanzees, and there are also species that target birds, other mammals, or different human body parts.

To spot head lice in a timely manner, you should know more about their development and morphology.

How Do Lice Look – Different Growth Stages

Head lice have three development stages. They start as nits or eggs and then go into the nymph stage before they reach full maturity (usually in a week or so). Each developmental stage has a different appearance.

Nits (Lice Eggs)

Before a louse egg hatches, it looks like a small brown (sometimes yellow or tan) dot on a hair. They usually hatch within two weeks, and the nit looks clear or white after hatching. It remains on the hair.

In most cases, the female louse positions the eggs near the scalp. However, this may vary in different climates because the embryo development depends on the temperature. For example, a female louse might lay the eggs 6 or more inches down the hair in warm climates. On the other hand, the eggs appear about 5mm from the scalp in cold weather.

The female secretes a special glue which contains keratin-like proteins to firmly attach to the hair. It is one of the reasons why the eggs are hard to remove.

A single female louse can lay up to four eggs per day. The eggs are oval and roughly 0.8mm long, and there is a miniature cap on top, which is breached once the louse hatches.


When lice hatch, they go through three molting stages before they reach full maturity. However, it can be quite tricky to spot the difference between a mature and a nymph louse because the metamorphosis process is subtle.

Size is the only visible difference. Adult lice have a longer abdomen compared to nymphs and it increases with each molting stage.

Some eggs might fail to hatch, especially if the humidity is not favorable. As nymphs have a voracious appetite (they feed on human blood), some may overeat and rupture their gut. This means that nymph mortality is very high during the first few days of their life.

Mature Lice

Mature head lice are 2.5 to 3.0mm long and quite flat. Their body is composed of the head, thorax, and abdomen. The sections of the thorax are fused together but they are clearly distinguishable from the abdomen and the head. Adult lice are grey but the color may differ depending on the environment and their abdomen appears reddish after feeding.

A fully-grown louse has a pair of eyes and antennae, which extend from its head. The lice mouth is perfectly designed for sucking blood and piercing the skin. But unless a louse is feeding, the piercing and sucking parts stay retracted within the mouth.

Both male and female lice have 6 legs which extend from the thorax. On male lice, the first pair of legs is a bit bigger to allow for easier copulation. All adult lice have a claw on each leg, which allows them to firmly hold onto the host’s hair. Despite the fact that lice cannot walk or jump, they are capable of climbing really fast and moving from one host to the other.

As for the abdomen, there are seven sections you might be able to distinguish. The last one contains the anus and genitals, and the first six have a pair of breathing spiracles each.

Interesting Fact: Female lice a bit larger than the males.

Other Lice Symptoms

In addition to the visible nits or lice, the infestation comes with a few other symptoms. Those affected usually experience a tickling sensation because the lice move around the head. This may cause itchiness and sores from excessive scratching.

It is not uncommon to feel irritated or have trouble sleeping, especially with children affected by lice. If any of these symptoms occur, wet your child’s hair and part it with a fine-toothed comb to check for lice. You should be able to see the miniature insect moving around and the nits appear to be cemented to the hair.

Treatment Options

When it comes to treatment, you can go for over-the-counter (OTC) shampoos or prescription medication. The OTC shampoos usually contain permethrin and pyrethrin, which effectively kill the lice after a few applications.

Prescription medications include benzyl alcohol lotion, malathion, or lindane shampoo. These medications are rubbed into the scalp/ hair and left for a few minutes before rinsing. The application itself is not challenging. But you need to follow the prescription instructions to the T to avoid eye and skin irritation.

In the case of infestation, it is also important to thoroughly wash the clothes that might be infected. The same goes for pillowcases, linen, or any other fabric that might come in contact with lice.

There’s a Scratch for Evey Itch

It is a common misconception that lice prefer dirty hair. In fact, they’d rather infect perfectly clean hair and scalp. Prevention isn’t always possible.

The good news is that is quite easy to spot them when you know what to look for. In the early (nit) stages, lice eggs might look the same as dandruff or common dirt. But unlike dandruff or dirt, lice cannot be easily combed out.

If you are not sure whether it’s lice or not, you should consult with a doctor, especially if there are other signs of infection, such as itching.