Head Lice: Symptoms, Treatment & How to Get Rid of Lice

What Are Head Lice and How Do They Spread?

Head lice (Pediculus humanus capitis) are tiny wingless parasitic insects that live exclusively on the human scalp, feeding on blood several times daily. They spread almost exclusively through direct head-to-head contact and cannot survive more than 24-48 hours away from a human host.

Head lice are one of the most common parasitic infestations affecting humans worldwide, particularly children between the ages of 3 and 11 years. In the United States alone, an estimated 6 to 12 million infestations occur annually among children in this age group. Despite their prevalence and the significant distress they cause to families, head lice are medically harmless parasites that do not transmit any diseases.

The presence of head lice has absolutely nothing to do with personal hygiene or cleanliness. These parasites are equal-opportunity infestors that can affect anyone regardless of their socioeconomic background, how often they wash their hair, or how clean their home is. In fact, some studies suggest that lice may actually prefer clean hair because it is easier for them to attach their eggs to smooth, clean hair shafts.

Understanding the biology of head lice is crucial for effective treatment and prevention. Adult head lice are approximately 2-3 millimeters long, roughly the size of a sesame seed, and are typically gray-brown in color. Their color can vary depending on how recently they have fed on blood. Female lice can lay up to 6-10 eggs (called nits) per day, cementing them firmly to individual hair shafts close to the scalp where the temperature is optimal for incubation.

How Do Head Lice Spread Between People?

Head lice spread primarily through direct head-to-head contact, which is why infestations are so common among school-age children who frequently engage in close contact during play, sharing tablets or phones, reading together, or during sports and sleepovers. The lice crawl from one head to another when hair from two people comes into contact.

Contrary to popular belief, head lice cannot jump, hop, or fly. They also cannot be transmitted to or from pets, as they are obligate human parasites that require human blood to survive. While it is theoretically possible for lice to spread through shared items like combs, brushes, hats, or headphones, this mode of transmission is considered rare because lice that fall off the head are typically weak and dying.

Lice that are found on furniture, carpets, or bedding are generally in a weakened state and unable to establish a new infestation. They lack legs adapted for walking on flat surfaces and cannot grip anything except hair strands. For this reason, extensive household cleaning is not necessary or recommended when treating a lice infestation.

What Are the Symptoms of Head Lice?

The most common symptoms of head lice include scalp itching (caused by an allergic reaction to lice saliva), a tickling sensation of something moving in the hair, visible lice or nits, and irritability or difficulty sleeping. However, many people have no symptoms at all, especially during the first infestation.

Recognizing the symptoms of head lice can be challenging because the signs can be subtle or absent entirely, particularly in first-time infestations. The most commonly reported symptom is scalp itching, but this itching is actually an allergic reaction to the saliva that lice inject when they feed, not a direct result of the bites themselves. This allergic response typically takes 4 to 6 weeks to develop in people who have never had lice before.

If someone has had head lice previously, their immune system recognizes the lice saliva, and itching can begin within just a few days of a new infestation. This means that adults and children who have had lice in the past may notice symptoms much sooner than those experiencing their first infestation. Conversely, some people never develop an allergic response and may carry lice for weeks or even months without any itching.

The lack of symptoms in many infected individuals is one of the reasons head lice spread so easily in school settings. Children and adults without symptoms can unknowingly transmit lice to others, making them "silent spreaders" of infestation.

Common Signs and Symptoms

• Scalp itching: Usually most intense behind the ears and at the nape of the neck where lice prefer to feed
• Tickling sensation: A feeling of something moving in the hair
• Visible lice: Adult lice can be seen moving through the hair, though they move quickly and avoid light
• Nits on hair shafts: Tiny oval eggs (about 1mm) attached firmly to hair, usually within 1cm of the scalp
• Red bumps or sores: From scratching, typically on the scalp, neck, and shoulders
• Small red spots: Where lice have been feeding
• Irritability and difficulty sleeping: Lice are more active in darkness
• Dark specks on pillow: May be lice feces or shed skins

What Do Lice and Nits Look Like?

Adult head lice are about 2-3 millimeters long, roughly the size of a sesame seed. They are wingless insects with six legs, each ending in a claw designed to grip hair. Their color varies from gray to brown to reddish, depending on when they last fed. After a blood meal, lice appear darker and more reddish.

Nits (lice eggs) are much smaller, about 0.8 millimeters long, and are oval-shaped. They are attached to hair shafts with a glue-like substance that makes them very difficult to remove. Live nits are typically dark (tan to brownish), while empty, hatched nits are white or clear. Nits are most commonly found within 1 centimeter of the scalp because they require body heat for incubation.

How Do You Check for Head Lice?

The most reliable method to detect head lice is wet combing with a fine-toothed lice comb over a white surface. Apply conditioner to wet hair to slow lice movement, then comb systematically from root to tip, checking the comb after each stroke for lice or nits.

Regular detection combing is the gold standard for finding head lice infestations. While visual inspection of the scalp can sometimes reveal an infestation, lice are small, fast-moving, and actively avoid light, making them difficult to spot with the naked eye. Systematic wet combing is far more effective and reliable.

The wet combing method, also called detection combing or bug busting, involves applying conditioner to wet hair and then combing through with a fine-toothed lice comb. The conditioner serves multiple purposes: it makes the hair easier to comb through, it immobilizes lice (slowing their movement significantly), and it makes lice and nits easier to see against the hair.

For optimal results, use a CE-marked (European certification) or similar quality lice comb with closely spaced metal teeth. Plastic combs may be less effective because their teeth can bend and allow lice to slip through. A light-colored comb will make it easier to see what you have caught.

Step-by-Step Detection Combing

1. Prepare materials: Fine-toothed lice comb, white paper or towel, hair conditioner, and good lighting
2. Wet the hair: Wash hair normally and apply a generous amount of conditioner
3. Section the hair: Divide into small, manageable sections using clips if needed
4. Start at the back: Begin at the nape of the neck where lice often congregate
5. Comb from root to tip: Place the comb flat against the scalp and draw firmly through to the end of the hair
6. Check the comb: After each stroke, wipe the comb on white paper or towel to examine for lice
7. Repeat systematically: Work through all sections, combing in multiple directions
8. Examine findings: Look for live lice (moving), nymphs (smaller), and nits attached to hair

When to Check for Lice

Consider checking for head lice when you notice any symptoms of itching or scratching, when there has been a lice outbreak at school or childcare, or when a family member or close contact has been diagnosed with lice. Additionally, regular routine checks before the start of a new school term can help catch and treat infestations early, before they spread further.

Summer months tend to see increased lice activity, so checking children before school starts in autumn is particularly important for preventing outbreaks. If one family member is found to have lice, all household members and close contacts should be checked.

How Do You Treat Head Lice?

Effective head lice treatment involves two applications of a medicated product (typically containing dimethicone) 9-10 days apart, combined with daily wet combing. Only treat if you find live lice. Continue daily combing for one week after the final treatment to confirm elimination.

Treatment for head lice should only be initiated when live lice are found through detection combing. Finding nits alone, without live lice, does not necessarily indicate an active infestation, as empty nit casings can remain attached to hair for months after successful treatment. Treating based solely on nit findings leads to unnecessary expense and exposure to treatment products.

The cornerstone of modern head lice treatment is the use of physically-acting treatments, particularly those containing dimethicone (a silicone-based compound). These products work by coating the lice and suffocating them, rather than through chemical pesticide action. This mechanism of action makes resistance virtually impossible, unlike older treatments that relied on insecticides.

Regardless of which treatment product you choose, two applications are essential for success. The first application kills live lice, but may not penetrate all eggs effectively. The second application, performed 9-10 days later, catches any lice that have hatched from surviving eggs before they are old enough to lay new eggs themselves. This timing is critical because lice eggs hatch in 7-10 days, and newly hatched lice (nymphs) cannot reproduce until they mature, which takes about 9-12 days.

Recommended Treatment Protocol

1. First treatment: Apply dimethicone-based product according to package instructions. Leave on for the recommended time.
2. Remove product: Comb through with lice comb to remove dead lice and eggs
3. Daily combing: Wet comb daily with conditioner to remove any surviving lice
4. Second treatment: Repeat product application 9-10 days after the first treatment
5. Continue monitoring: Comb daily for one week after second treatment, then twice more over the following week

Types of Treatment Products

Dimethicone-based products (Recommended): These physically-acting treatments are the first-line recommendation from most medical authorities. Dimethicone coats the lice, blocking their respiratory system and causing death through suffocation. They are generally safe, effective, and resistance is not a concern.

Benzyl benzoate with disulfiram: This combination is available as an alternative if dimethicone products are not effective. It should be massaged into the hair and left for 24 hours before washing out. Two treatments are required.

Permethrin and other insecticide-based products: While still available, these older treatments are increasingly affected by resistance in lice populations. They work by attacking the nervous system of lice but are becoming less effective in many areas.

What If Treatment Does Not Work?

If you continue to find live lice after completing the full two-treatment protocol, there are several possible explanations. The most common reason is incomplete application of the product, particularly if hair was not fully saturated or if the product was not left on for the recommended duration. Reinfestation from untreated contacts is another frequent cause of apparent treatment failure.

If you have followed the treatment instructions carefully and ruled out reinfestation, the lice may be resistant to the particular product used. In this case, switch to a different type of treatment product. If problems persist after trying multiple products, consult a healthcare provider for further guidance.

How Do You Comb Out Head Lice Properly?

To properly comb out head lice, apply conditioner to wet hair, divide into small sections, and comb each section from root to tip using a fine-toothed metal lice comb. Work systematically from the back of the head forward, wiping the comb on white paper after each stroke to check for lice.

Wet combing is not just a detection method but also a crucial part of treatment. When combined with medicated products, regular combing physically removes lice and eggs that the treatment may have missed. Some families choose wet combing as their sole treatment method (called "bug busting"), which can be effective but requires consistent daily combing for at least two weeks.

The technique of combing matters significantly for effectiveness. Simply running a comb through the hair a few times will not catch most lice. Instead, systematic, thorough combing of every section of hair is necessary. The process typically takes 15-30 minutes depending on hair length and thickness.

Detailed Combing Instructions

Back of the head: Start by creating a vertical part down the center back of the head. Comb all hair on one side of the part, then the other, working from the bottom up. The nape of the neck is a favorite location for lice, so be especially thorough here.

Top of the head: Create horizontal parts and comb each section thoroughly, working from back to front. Comb from multiple angles to ensure no area is missed.

Sides and front: Work from the hairline backward, then from the back forward. Pay attention to behind the ears, another common lice location.

Throughout: After each comb stroke, wipe the comb on white tissue or paper. Look for live lice (which may still be moving), dead lice, nymphs (baby lice, which are much smaller), and nits. Rinse the comb in water between sections if debris builds up.

How Can You Prevent Head Lice?

Preventing head lice primarily involves avoiding head-to-head contact and not sharing personal items that touch the head. Regular detection combing helps catch infestations early. There is no evidence that preventive treatments or special shampoos reduce the risk of infestation.

True prevention of head lice is challenging because the primary mode of transmission, direct head-to-head contact, is difficult to avoid, especially among children. However, understanding how lice spread can help reduce the risk of infestation and prevent outbreaks from spreading further within families and schools.

While various "prevention" products are marketed, including special shampoos, sprays, and treatments, there is limited scientific evidence that any of these products significantly reduce the risk of infestation. The most effective preventive measure remains regular detection combing to catch infestations early, before they can spread to others.

Practical Prevention Strategies

• Avoid head-to-head contact: Teach children to avoid touching heads during play, taking selfies, or sharing screens
• Do not share personal items: Combs, brushes, hair accessories, hats, and headphones should not be shared
• Tie back long hair: Keeping long hair tied back or braided may reduce direct hair contact
• Regular detection combing: Weekly checks during outbreaks, monthly checks routinely
• Inform others: If your child has lice, inform the school and close contacts so they can check and treat if needed
• Check before school: Especially important at the start of the school year and after summer camps

Do You Need to Clean the House?

Extensive house cleaning is not necessary and not recommended when treating head lice. Because lice cannot survive more than 24-48 hours without a human host and cannot reproduce without human blood, environmental cleaning has minimal impact on treating or preventing reinfestation.

Reasonable precautions include washing recently used pillowcases and any hats or hair accessories worn in the past 48 hours in hot water (at least 60C/140F). Combs and brushes should be soaked in hot water for at least 10 minutes. Items that cannot be washed can be sealed in a plastic bag for 48 hours, though this is generally unnecessary.

Vacuuming furniture and floors is not recommended specifically for lice control, though normal household cleaning is fine. Fumigating or using insecticide sprays in the home is never necessary or recommended for head lice treatment.

When Should You See a Doctor for Head Lice?

Most head lice infestations can be successfully treated at home. See a healthcare provider if treatment fails after multiple attempts, if skin becomes infected from scratching, if the affected person is under 2 years old, or if you are unsure whether the person actually has head lice.

The vast majority of head lice cases can be managed effectively at home with over-the-counter treatments and wet combing. Healthcare professional involvement is rarely necessary. However, certain situations warrant medical consultation to ensure proper diagnosis and treatment.

Secondary bacterial skin infection is the main medical complication of head lice infestation. This occurs when excessive scratching breaks the skin, allowing bacteria to enter. Signs of skin infection include increasing redness, warmth, swelling, pain, or pus at scratch sites. If you notice these symptoms, especially if accompanied by fever, seek medical care promptly.

Reasons to Consult a Healthcare Provider

• Treatment has failed despite correct application of multiple products
• Signs of skin infection (redness, swelling, pus, increasing pain)
• The person with lice is under 2 years of age (treatment options are limited)
• Uncertainty about whether it is actually head lice
• The person is pregnant or breastfeeding and unsure about treatment safety
• Severe allergic reaction to treatment products

Summary: Steps to Get Rid of Head Lice

To eliminate head lice: confirm infestation with wet combing, inform close contacts, treat all affected individuals simultaneously with a dimethicone-based product twice (9-10 days apart), comb daily during treatment, and continue monitoring for two weeks after the final treatment.

Successfully eliminating head lice requires a systematic approach combining proper detection, effective treatment, and diligent follow-up. Here is a comprehensive action plan for dealing with a head lice infestation.

Complete Action Plan

1. Confirm the infestation: Use wet combing with conditioner and a fine-toothed lice comb to find live lice. Only proceed with treatment if you find live, moving lice.
2. Inform contacts: Notify the school, childcare center, and families of close friends so they can check and treat if necessary. Everyone who may have been in head-to-head contact should be checked.
3. Check all household members: Perform wet detection combing on everyone in the household. Treat all affected individuals simultaneously to prevent re-infestation.
4. Apply first treatment: Use a dimethicone-based product according to package instructions. Ensure hair is fully saturated and leave on for the recommended time.
5. Comb daily: Perform wet combing with conditioner every day to remove any surviving lice. This is essential for treatment success.
6. Second treatment at day 9-10: Apply the same treatment product again to kill any lice that hatched from eggs that survived the first treatment.
7. Continue daily combing: Keep combing daily for one week after the second treatment.
8. Final checks: Comb at least twice more over the following week. If no live lice are found, the infestation is cleared.