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The Facts of Lice: Head Lice

The Facts of Lice: Head Lice

With many children back in school already, it's time to address an important condition that spreads like wildfire, especially amongst children. Head Lice, or Pediculosis, is an infestation of a human parasitic lice, which feed exclusively on human blood. 

The head louse, or pediculus humanus capitus, can be found on the head, eyebrows, and eyelashes of people. Head lice feed on the human blood several times a day, and live close to the scalp. Though they are not known to spread disease, head lice lay eggs on body hairs or clothing fibers.

After the eggs, or nits hatch, lice must feed within 24 hours or they will die. Lice crawl and attach superficially to the skin and hair. One female louse deposits approximately 60 to 150 eggs to hair shafts. Nits survive by ingesting the blood from the human host. A louse bite injects a toxin into the skin, causing mild irritation and a purpuric spot. Repeated bites can cause a sensitization to the toxin, which then leads to more serious inflammation.



Head lice are found worldwide. In the United States, infestation with head lice is most common around pre-school children who attend daycare, elementary school children, and household members of the infested children. An estimated 6 to 12 million infestations occur each year in the United States among children 3 to 11 years old. 

Head lice move by crawling, as they cannot hop or fly. Head lice are spread by direct contact with the hair of an infested person. Anyone who comes in head to head contact with someone who already has head lice, is at the greatest risk. Spread by contact with clothing, such as: hats, scarves, coats, or other personal items, such as: combs, brushes or towels - used by an infested person is uncommon. Contrary to popular belief, personal hygiene or cleanliness in the home or school is not a factor in contracting head lice.

What Does Head Lice Look Like?

Egg/Nit: Nits are lice eggs laid by the adult female head louse at the base of the hair shaft, near the scalp. Nits are firmly attached to the hair shaft and are oval-shaped, very small, and hard to see. Nits often appear to be yellow or white, though they can appear to be the same color as the hair of the infested person. Nits are often confused with dandruff, scabs, dirt particles or hair spray droplets. Head lice nits usually take about 8-9 days to hatch, and the ones that do hatch, are most likely located a quarter of an inch away from the base of the hair shaft. Nits that are located further than a quarter of an inch away from the base, may already be hatched, non-viable nits, or empty nits. This is very difficult to distinguish with the naked eye.

Nymph: A nymph is an immature louse that hatches from the nit. A nymph looks like an adult head louse, but is smaller. To live, a nymph must feed on blood. They mature into adults approximately 9-12 days after hatching from the nit.

Adult: The fully grown and developed adult louse is about the size of a sesame seed, has 6 legs, and is tan to grayish-white in color. Adult head lice may look darker in people with dark hair, from those with light hair. To survive, adult head lice must also feed on blood. An adult head louse can live to 30 days on a person's head, but will die within 1-2 days if it falls off of a person. Adult female head lice are usually larger than males, and can lay around 6 eggs per day.

Where is Lice Most Commonly Found?

Head lice and head lice eggs are found almost exclusively on the scalp, especially around and behind the ears, and near the neckline at the back of the head. Head lice or the eggs can sometimes be found on the eyelashes or eyebrows, but that is less likely. Head lice hold tightly to hair with hook-like claws that are at the end of each of their 6 legs. Head lice eggs are cemented firmly to the hair shaft and can be difficult to remove.

Signs & Symptoms of Head Lice


1. Tickling feeling of something moving throughout the hair.

2. Itching, which would be caused by an allergic reaction to the bites of the head louse. 

3. Irritability and difficulty sleeping, as head lice are most active in the dark. 

4. Sores on the head that are caused by scratching. These sores can sometimes become infected with bacteria found on the person's skin.

How Does One Get Lice?

As mentioned above, head to head contact with an already infested person is the most common way to get head lice. Head to head contact is common during recess or play at school, home, daycare, or elsewhere. 

Although less common, head lice can be spread by sharing clothing or personal belongings. This happens when lice crawl, or nits attached to shed hair hatch, and fall onto the shared clothing or item. For example: shared clothing includes,

- hats, scarves, coats, sports uniforms, shirts, etc.,

Examples of articles shared include: hair ribbons, barrettes, combs, brushes, towels, stuffed animals, etc., recently worn or used by an infested person. 

One can also get lice simply by lying on a bed, couch, pillow, or carpet that has recently been in contact with an infested person. 

Dogs, cats, and other animals/pets do not play a role in the spread of head lice. 


The diagnosis of a head lice infestation is best made by finding a live nymph or adult louse on the scalp or hair of a person. However, because nymphs and adult lice are very small, move quickly, and avoid light, they can be difficult to find. Using a magnifying lens and/or a fine-toothed comb may be helpful to find live lice. If crawling lice aren't seen, finding nits firmly attached to the base of the hair shafts strongly suggests that a person is infested and should be treated. 

If you are not sure if a person has head lice, the diagnosis should be made by a healthcare professional, local health department, or other trained personnel to identify live head lice. 


Treatment for head lice is recommended for people diagnosed with an active infestation. All household members and close contacts should be checked, and those with evidence of an active infestation should be treated. Some experts believe that prophylactic treatment is best for people who share the same bed with actively-infested people. All infested people, including household members and close contacts, should be treated at the same time.

Some medicines that kill lice can kill the eggs. This is called an ovicidal effect. For medicines that are only weakly ovicidal or not ovicidal, routine treatment is recommended. For those that are more strongly ovicidal, retreatment is recommended only if live lice are still present several days after treatment. To be most effective, retreatment should occur after all eggs have hatched, but before new eggs are produced.

When treating head lice, supplemental measures can be combined with recommended medicine; however, such additional measures generally are not required to eliminate a head lice infestation. For example, hats, scarves, pillow cases, bedding, clothing, and towels worn or used by the infested person in the 2-day period just before treatment is started can be machine washed and dried using the hot water and hot air cycles. Lice and eggs are killed by exposure for 5 minutes to temperatures greater than 53.5 degrees Celsius or 128.3 Fahrenheit.

Items that cannot be laundered may be dry-cleaned or sealed in a plastic bag for two weeks. Items such as hats, grooming aids, and towels that come in contact with the hair of an infested person should not be shared. Vacuuming furniture and floors can remove an infested person’s hairs that might have viable nits attached.

Treating the Infested Person(s)

Requires using an OTC or prescription medicine. Follow these treatment steps below:

1. Remove clothing that can become wet or stained during treatment.

2. Apply lice medicine, according to the instructions contained in the box or printed on the label. If the infested person has long hair (longer than shoulder length), it may be necessary to use a second bottle. Pay close attention to instructions on the label or box regarding how long the medication should be left on the hair, and how it should it washed out.

Note: Don't use a combination shampoo/conditioner before using lice medicine. Don't rewash the hair for 1-2 days after the lice medicine is removed.

3. Have the infested person put on clean clothing after treatment.

4. If a few live lice are still found 8-12 hours after treatment, but are moving more slowly than before, do not retreat. The medicine may take longer to kill all of the lice. Comb dead and any remaining live lice out of the hair using a fine-toothed nit comb.

5. If, after 8-12 hours of treatment, no dead lice are found and they seem as active as before, the medicine may not be working. Do not retreat until speaking with a health care provider, as a different medication may be necessary.

6. Use a nit comb, which are often found in lice medicine packages, to comb nits and lice from the hair shaft. Many flea combs made for pets are also effective.

7. After each treatment, checking the hair and combing with a nit comb to remove nits and lice every 2-3 days may decrease the chance of re-infestation. Continue to check for 2-3 weeks to be sure all lice and nits are gone.

8. Retreatment is meant to kill any surviving hatched lice before they produce new eggs. For some drugs, retreatment is recommended routinely about a week after the first treatment, and for others only if crawling lice are seen during this period. Retreatment with a lindane shampoo is not recommended.

Supplemental Measures: head lice don't survive long without being able to feed. Follow the steps below to avoid re-infestation by lice that have recently fallen off the hair or crawled onto clothing or furniture.

1. Machine wash and dry clothing, bed linens, and other items that the infested person wore or used during the 2 days before treatment, using the hot water (130 degrees Fahrenheit) laundry cycle, and the high heat drying cycle. Clothing and items that are not washable can be dry-cleaned, or sealed in a plastic bag and stored for 2 weeks. 

2. Soak combs and brushes in hot water (at least 130 degrees F) for 5-10 minutes.

3. Vacuum the floor and furniture, particularly where the infested person sat or lay. However, the risk of getting infested by a louse that has fallen onto a rug or carpet or furniture is very small. Head lice survive less than 1–2 days if they fall off a person and cannot feed; nits cannot hatch and usually die within a week if they are not kept at the same temperature as that found close to the human scalp.

4. Do not use fumigant sprays, as they can be toxic if inhaled or absorbed through the skin. 

Over the Counter Medications

Many head lice medications are available without a prescription at a local drug store or pharmacy, Each OTC product approved by the FDA for treatment contains Pyrethrin's and Permethrin lotion

Prescription Medications

The following medications are FDA approved and only available by prescriptionBenzyl Alcohol Lotion, Ivermectin Lotion, Malathion Lotion, and Spinosad Topical Suspension. 

Lindane shampoo should only be used as a second-line treatment.

When treating head lice, do not use extra amounts of any lice medication unless instructed to do so by a physician and pharmacist. The drugs used to treat lice are insecticides and can be dangerous if they are misused or overused. All medications should be kept out of the eyes. If they do get into the eyes, they should be immediately flushed away. 

Do not treat an infested person more than 2-3 times with the same medication if it doesn't seem to be working. This may be caused by using the medicine incorrectly or by resistance to the medicine. Always seek the advice of your health care provider if this should happen. He/she may recommend an alternative medication. Do not use different head lice drugs at the same time unless instructed to do so by your physician and pharmacist.

Before stopping or starting any treatment for head lice, be sure to consult a local physician. Here at Mountainside Medical Equipment, we offer several treatments for head lice. Please visit our head lice page to browse the products, or feel free to call one of our friendly and knowledgeable customer service associates for more information. 

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tony - November 21, 2019

I’ve been looking for
lice killer spray but they were all made of chemicals.
after reading,I realized that you can combat it
through natural methods which repel them. You don’t need to kill them if they aren’t there, duh.

tony - November 21, 2019

Thank you for the blog it was very informative. Check this out
lice killer spray I did not realize there were so many different ways to approach one problem. it will help you out in killing pests and keep the head free of infestations.

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