Head lice – Definition, types and symptoms

Lice are parasites in the form of small insects that live in human hair and suck the blood of the scalp. Head lice infection is called pediculosis. Infestation with head lice is medically known as Pediculosis capitis. The Centers for Disease Control and Prevention (CDC) estimates that up to 12 million head lice infestations occur annually in the United States.

Adult female lice can lay eggs up to six eggs every day. Ticks lay eggs and are placed right on the hair shaft. Ear lice that are less than six millimeters from the scalp are likely to hatch. Eggs basically stick to the hair by secretions from female lice.

It takes about a week for the eggs to hatch, producing nymphs. The nymph then passes through three successive bursts of growth. During these bursts, they molt until they reach adult size.

Adult fleas are the size of sesame seeds and are very difficult to see, because they are white to brown. Head lice usually suck blood four to five times every day. They use parts of their mouth to bite the skin and secrete substances that function to block clotting. Although it is important to note that head lice infestation can happen to anyone, some people have a higher risk of contact with head lice.

Types of Head Lice

Three types of lice live in humans, including:

  • Head lice, usually found in hair, most often behind the neck and behind the ears. Head lice are common in preschool age and elementary school age children. Adults can also infest these fleas too, especially adults who live with children.
  • Pubic lice, also called crabs, are usually found in the pubic area. But they can also be found in facial hair, in eyelashes, in eyebrows, in the armpits, in chest hair, and on the scalp, but rarely.
  • Body lice, live and lay eggs in layers of clothing. Fleas only occur in the body when they eat.

Head lice spread easily from one person to another through contact or through shared clothing or personal items, such as hats or combs. Fleas cannot jump or fly.

Symptoms of Head Lice

The most common symptom of head lice is itching, which is caused by an allergic reaction. Fleas bite the skin to suck someone’s blood. Saliva from these bites causes allergic reactions and itching.

Itching may not occur immediately, depending on one’s sensitivity and history of lice. The first time someone is infested with lice, it may take several weeks or months to become itchy and begin to notice. In the case of recurrent lice, a person may start to itch within 2 days because the immune system reacts faster given the exposure has happened before.

Some people become very sensitive to flea bites and have unbearable itching. Others will develop tolerance to bites and have a slight itching or no itching at all, even when the hair has back lice. Aside from itching, the symptoms of lice hair vary depending on the type of lice.

Head lice may not cause any symptoms at first. Itching on the scalp can start weeks or even months after the lice have started to spread. Scratching can make the skin peel. Raw skin may be clear liquids or crust above, and may be infected.

Pubic lice cause severe itching. Their bites can cause small marks that look like bruises on the back of the body, thighs, or upper arms. If pubic lice are found on the eyelashes, the edges of the eyelids can be skinned. You might see lice and eggs at the base of the eyelashes.

Body lice cause very bad itching, especially at night. Itchy sores appear on the armpits and on the waist, chest, and other areas where stitches of clothing press against the skin. Head lice and eggs can be found in a person’s clothing layer but are usually not seen on the skin. Frequent scratching can cause skin infections. In the most severe cases of head lice, hair may fall out, and the skin can be darker in areas full of lice.

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