Itching is the most common symptom of head lice. People who have head lice for the first time may not feel itchy right way. It can take 4 to 6 weeks for itching to start.

You may be able to see lice, but they move quickly, avoid lights and are small. You may also see lice eggs on hair shafts. Also called nits, lice eggs stick to hair shafts. They are easiest to see around the ears and hairline of the neck. But they are tiny so it may be easier to see empty nits, especially on darker hair. Empty nits are lighter in color and further from the scalp.

Seeing empty nits doesn't mean there are live lice. That's especially true if the nits are greater than 1/4 to 3/8 inches (6 to 9.5 millimeters) from the scalp.

Sores on the scalp, neck and shoulders are another symptom. Scratching can lead to small bumps that appear red on white skin and may be harder to see on Black or brown skin. These sores may get infected.

Most people who have head lice don't need to contact a healthcare professional. But if you think you or your child has lice, a member of your healthcare team can confirm the presence of head lice and suggest the best treatment.

If you aren't sure if you or your child has head lice, see a healthcare professional. It's easy to mistake other things for nits, including:

• Dandruff.
• Hair products, such as hair spray droplets.
• Beads of dead hair tissue on a hair shaft.
• Scabs, dirt or hair changes from a fungal infection.
• Other small insects that might be in the hair.

Head lice infestation is most often caused by direct contact with these insects. Head lice are a tan or gray insect about the size of a sesame seed. The female louse sticks each egg to the base of a hair shaft less than 1/8 inch (3 millimeters) from the scalp.

The louse life cycle

A louse goes through three stages:

• Eggs, also called nits, that hatch after 7 to 12 days.
• Nymphs, immature forms of lice that become mature adults after about seven days. The nymphs also feed on blood from the scalp.
• Adult lice, which can live for 3 to 4 weeks. The female louse lays up to 10 eggs a day.

Transmission

Head lice crawl, but they can't jump or fly. Head lice most often spread from one person to another by head-to-head contact. This often happens within families or among children who have close contact with each other.

It's less common for head lice to spread without direct contact. But lice may spread from one person to another through items they share if one person is infected. Items include:

• Clothing, such as hats, scarves and sports uniforms.
• Brushes and combs.
• Items worn in the hair, such as headphones, hair clips, headbands and ribbons.
• Pillows, towels, stuffed animals and the fabric that covers furniture.

Household pets, such as dogs and cats, don't spread head lice.

Head lice infect hair of any length and type. Head lice spread mainly by direct head-to-head contact. So the risk of spreading head lice is greatest among children who play or go to school together. In the United States, head lice most often happen in children in preschool through grade school.

When people scratch the itch that head lice cause, the skin may break. The broken skin may get infected.

You can stop the spread of lice by avoiding hair and head contact between people. The chance of spreading head lice from items that come in contact with the hair or head is small. But you can lower your risk of getting head lice by taking some precautions.

• Don't share hair styling tools like brushes, ribbons or clips.
• Don't share hats or scarves.
• Don't encourage hair contact during sports, at playtimes or when kids are together for activities.
• Don't lie on beds, couches or pillows that a person who has head lice has been on recently.
• Don't share fabric items that a person who has had lice has used in the two days before getting treated.

Do use or allow your child to use protective headgear for sports or bicycling. Don't let a fear of head lice stop you from using these important safety items.

To diagnose a head lice infestation, you or a healthcare professional look for lice at any stage of the life cycle. Young lice or adults may be seen or collected with a comb. The fine-toothed comb, called a nit comb, is used from the scalp to the end of the hair. Guidelines suggest looking at wet hair that's coated with hair conditioner or other products.

Identifying nits

Check for nits at the hairline, especially behind the ears. A live nit needs to be near the scalp to survive. Nits found more than about 1/4 inch (6 millimeters) from the scalp are likely dead or empty. Use a magnifying lens or glass to make sure what you’re looking at is head lice eggs. Or see a healthcare professional who can help identify nits.

To kill head lice and lice eggs, you can use a few methods. Wet combing, smothering or dehydrating are ways to kill head lice. Or you can use medicine available with or without a prescription. The medicine may not kill the newest eggs. So a second treatment at the right time to kill nymphs may be needed.

Depending on the medicine you use, most often you treat again 7 to 10 days after the first treatment. Ask a member of your healthcare team to write down the treatment schedule.

Medicine you can get without a prescription

Follow all product label directions and do not use more than the label or your healthcare professional says to use. And don't use more than one head lice treatment medicine at a time. The side effects of all the products put on the scalp may include itching and mild burning of the scalp that can last for days.

• Permethrin (Nix) or products that have pyrethrin (Rid, Pronto Plus, others). Follow the package directions for use of these products for people age 2 months or older. Then remove nits with the comb included in the package. Repeat the treatment 9 to 10 days later. Keep combing out the nits every 2 to 3 days for 2 to 3 weeks. Make sure no nits are left on the scalp.
• Ivermectin (Sklice). You can use this lotion for adults and children age 6 months or older. You apply it once to dry hair. Rinse with water after 10 minutes. Don't use it again without talking with a healthcare professional.

Prescription medicines

In some parts of the world, medicines available without a prescription no longer kill lice. Also, these medicines can fail if you don't use them correctly or repeat them as instructed.

If the correct use of a treatment you get without a prescription has failed, your healthcare professional may suggest prescription treatments. These include:

• Spinosad (Natroba). Spinosad is for adults and children age 6 months and older. Apply to dry hair. Leave on for 10 minutes. Rinse with warm water over a sink to keep the lotion from getting on the skin. Don't shampoo hair for 24 to 48 hours. Repeat in seven days if you see lice.
• Malathion. Malathion is for adults and children age 6 years and older. Put the lotion on the hair and leave it on for 8 to 12 hours. Then rinse it out using warm water over a sink to keep it from getting on the skin. Don't shampoo hair for 24 to 48 hours. Repeat in seven days if you see lice.

  This medicine is flammable, which means it can cause fires. Don't use it with a hair dryer or curling iron or near an open flame.

• Ivermectin (Stromectol). This is a prescription that you take by mouth. You can give it to children who weigh more than 33 pounds (15 kilograms) if topical treatments don't rid the scalp of head lice. You can repeat it in 7 to 10 days if needed.

Wet Combing

Combing wet hair with a fine-toothed nit comb may remove lice and some nits. You can do this after treatment of the scalp with a medicine or in place of a medicine. Start by wetting the hair or coating it with hair conditioner or other products that can slow lice. Some options are products with dimethicone, mayonnaise, or petroleum jelly.

Do not use household products that aren't meant for humans, anything that could catch fire easily or chemicals that can irritate the skin.

Smothering agents

Some people use household products to keep head lice from getting air. These products include mayonnaise, margarine or butter, or petroleum jelly. People put a lot of the product on the hair, cover the head with a shower cap and leave it on overnight. It's not clear how well these products work.

Dehydration

Another treatment is a machine that uses hot air to kill head lice and their eggs by drying them out. This process is called dehydration or desiccation. People who run the machines need special training. Professional lice treatment centers may offer these machines.

Don't try to use a hair dryer to get rid of lice. A hair dryer can send lice into the air, so they may spread to another person.

If you don't want to treat head lice with medicine, you may think about trying a home treatment. But there's little to no proof that home treatments work.

Products to avoid

Never use products that can cause fire, called flammable products, to kill lice or to remove nits. Such products include kerosene or gasoline. Don't use products made for animals, such as flea shampoos.

Essential oils

Natural plant oils, such as limonene and thymols, damage the nervous system of insects when used in insecticide products. Based on this idea, some essential oils were thought to be useful in preventing head lice infestation or killing lice on the scalp.

But these products aren't produced with the same standards as medicines. Head lice medicines are tested to make sure they work and that they're safe. Essential oils aren't regulated in the same way and may cause allergic reactions.

Household cleaning

Lice most often don't live past a day or two without feeding from a human scalp. And eggs can't survive without the warmth near the scalp. So the chance of lice staying alive on household items is small.

Still, it's a good idea to clean items that an affected person has used in the past two days. To clean items, follow these tips:

• Wash items in hot water. Wash bedding, stuffed animals and clothing in hot, soapy water. The water should be at least 130 degrees Fahrenheit (54.4 degrees Celsius). Dry on high heat.
• Soak hair care items in hot water. Clean combs, brushes and things that go in the hair by soaking them in hot, soapy water for 5 to 10 minutes.
• Seal items in plastic bags. Seal items that can't be washed in plastic bags for two weeks.
• Vacuum. Go over the floor and furniture. Mainly vacuum the places where the person with lice has been sitting or lying down.

If you think you or your child has head lice, you may start by seeing your family's healthcare professional or your child's pediatrician.

Here's some information to help you get ready for your appointment.

What you can do

Before your appointment, make a list of:

• The symptoms and when they began.
• All medicines, vitamins and other supplements you or your child takes, including the dosages.
• Questions to ask your healthcare professional.

Basic questions to ask about head lice include:

• What's likely causing the symptoms?
• Other than the most likely cause, what else might cause the symptoms?
• How can you tell if there are lice?
• What's the best course of action?
• What happens if the treatment doesn't work?

Be sure to ask all the questions you have.

What to expect from your doctor

Your healthcare professional is likely to ask you questions, such as:

• When did your symptoms begin?
• Have your symptoms been continuous or occasional?
• How bad are your symptoms?
• What, if anything, have you tried to ease the symptoms?

What you can do in the meantime

The person with head lice should not have head-to-head contact with anyone.