Lice are tiny creatures that attach to humans, feed on blood, and can be passed easily through close contact. According to the Centers for Disease Control and Prevention (CDC), an estimated 6 to 12 million lice infestations occur each year in the United States, most commonly among children between 3 to 11 years of age, members of their household, and their caretakers.
Lice is the second most common communicable disease (following the common cold) among school-aged children in the US. A recent study found evidence supporting the increased incidence of lice in states with a warmer climate, including states such as California, Florida, Georgia, and Texas.
Anyone can contract and pass along lice, although certain factors may predispose patients to becoming a host for lice. Head lice do not spread any disease, although body lice have been known to spread several diseases. Secondary bacterial infections may also arise due to the frequent scratching exhibited by many patients suffering from lice irritation.
What are Lice?
Lice are small, wingless, parasitic insects that live on humans and feed on blood for survival. When many lice (louse) live and multiply on a host, it is known as an infestation (pediculosis.) Lice can only be spread from person-to-person through close contact or sharing of clothes, brushes, hats, and other personal items. Lice cannot fly or jump, so they move by crawling. Humans can only get lice from other humans, and cannot contract lice through contact with dogs, cats, or other animals.
There are three types of human lice – head lice, body lice, and pubic lice. Each of the three types of lice infections are caused by a unique parasite, produce different symptoms, and are diagnosed and treated differently.
Head lice, also known as pediculus humanus capitis, is the most common type of lice. These lice are found in the hair and scalp. They can be seen from the nape of your neck and over your ears. They are typically 2.1-3.3 mm long, and attach their eggs (“nits”) to the base of the hair shaft, typically about 10 nits per day. Head lice are a grey-white color, and females have a lifespan of about one month. Head lice nits hatch after 6 to 10 days, becoming nymphs, and then become adult head lice 10 days later.
Head lice do not spread disease, and are most active in the dark. A common misconception is that poor hygiene leads to head lice infestations. In fact, there is no association between hygiene, socioeconomic status, and head lice. Young, school-aged children are more likely to contract head lice, due to their close contact during play time, and their frequent sharing of personal items such as toys. Young girls contract head lice more often than young boys, most likely due to sharing of brushes, hair ties, and frequent head-to-head contact. Recent research has investigated different types of lice, and has found particular species of head lice with claws that are better adapted for grasping certain types of hair (shape and width) versus others. African Americans are less likely to contract lice than patients from other backgrounds.
Body lice, also known as pediculus humanus corporis or clothes louse, live in clothing, typically within the seams, and can also be found on bedding. They crawl to human skin to feed on blood. Body lice are slightly larger than head lice, measuring 2.3-3.6 mm long, and are shaped similarly to head lice. This type of lice is more commonly associated with poor hygiene (unable to bathe or clean clothes regularly,) poverty, and overcrowded areas. Unlike head lice, body lice have been known to transmit several diseases, including typhus, trench fever, and relapsing fever.
Pubic lice, also known as pthirus pubis or “crab” lice, is transmitted through sexual or intimate contact, and condoms do not prevent their transmission. They are 1.1-1.8 mm in length and have a distinctive shape, rounded with three pairs of legs on each side of their bodies (crab-like appearance). Public lice are typically found in the pubic area, but can also be found on facial hair, eyelashes, eyebrows, armpit hair, chest hair, and the scalp (in rare cases.) Female pubic lice live for shorter periods of time and lay fewer numbers of eggs than female head lice and body lice. Their typical lifespan is three weeks, laying approximately 3 eggs per day. Pubic lice eggs incubate for 6 to 8 days before hatching. After a pubic lice infestation, the patient may develop a blue-colored sore around the affected area. Pubic lice cannot be spread through contact with toilet seats.
What Causes Lice?
A lice infestation is caused by parasitic lice living on skin, feeding on blood, and laying eggs on the human body. Lice can be caused by different factors depending on the type of lice you contract.
Head lice is most commonly caused by head-to-head direct contact. Members of the same household, and caregivers of patients with lice, are at high risk for contracting lice. Others who play or closely interact with patients with lice have an increased chance for contracting lice, such as school teachers and classmates.
Other methods of contracting head lice include sharing personal items such as:
- Hair brushes, combs
- Toys (such as stuffed animals)
- Furniture (carpets, couches)
Storing lice-infested items near clean items in a closet, locker, or side-by-side hooks, may increase the chance that lice can crawl and settle on clean items. Although lice require human blood for survival, they can live for up to 2 days without a human body host.
Body lice (clothes lice,) similarly to head lice, can be contracted through close contact with lice-infested items – such as bedding and clothing. Body lice live on clothing, and crawl to the human body to feed on blood. Body lice is also associated with poor hygiene, lower socioeconomic status, poverty, military barracks, refugee camps, and spending time in overcrowded areas.
Pubic lice can be contracted through sexual, or very close intimate contact. This type of lice is most commonly found in adults. Pubic lice found in children may be a sign of sexual abuse.
Signs and Symptoms of Lice
The most common symptom of a lice infestation is itchiness. Close inspection of hair, clothing, and the body may show visible lice or eggs. Using a fine-toothed comb or a black light (Wood’s Lamp Exam) may help detect the presence of lice and their eggs.
Nits, or lice eggs, may sometimes be mistaken for dandruff. Unlike dandruff, lice eggs are not easily able to be brushed away from hair.
Symptoms of lice may vary, depending on which type of lice you have contracted.
Some head lice infestations may be asymptomatic at first, and slowly become itchy. Amount of itchiness may depend on a person’s level of sensitivity and history of previous lice infestations. First time cases of lice may take more time to become symptomatic (up to several weeks or even months,) while repeat cases of a lice infestation may produce symptoms as early as within a few days of an infestation.
Symptoms of head lice include:
- Scalp itchiness
- Tickling feeling from movement of hair
- Small red bumps on the scalp, neck, and shoulder area
- Sores from constant scratching
- Difficulty sleeping (head lice are most active in the dark)
- Swollen, tender, and enlarged lymph nodes
Signs of body lice include:
- Bad itchiness, particularly at night
- Itchy sores appearing around the armpits, waist, torso (where seams of clothing can press against skin)
- Lice and eggs visualized near the seams of clothing and bedding
Symptoms of pubic lice include:
- Severe itchiness, especially around the genitals, torso, thighs, upper arms
- Bite marks that look like small bruises on the torso, thighs, upper arms
- Eyelid irritation
- Crusty eyelids
Because pubic lice is contracted through sexual contact, it may also be accompanied by a sexually transmitted infection (STI). STI symptoms may present along with symptoms of public lice. Patients may experience burning, itching, and tingling near the genitals.
Frequent scratching from an itchy lice infestation may cause a skin infection. This may cause skin to become raw, a clear fluid to “ooze” from the affected area, or even become more seriously infected. Some severe cases of lice may cause hair to fall out or skin to become darker due to the lice infestation.
Prevention of Lice
Caretakers and members of the same household of a person with lice should all be carefully checked for lice or nits.
Helpful methods to lessen the chance of, or prevent, a lice infestation include the following:
- Avoid head-to-head contact during playtime, sports, or other activities
- Avoid sharing hair brushes, combs, hats, pillows, scarves, uniforms, helmets, hair ribbons, hair barrettes, and clothing
- Disinfect combs and brushes (especially if used by an infected person) by soaking them in hot water (130 degrees F, 54.44 degrees C) for 5-10 minutes
- Avoid contact with beds, sheets, carpets, pillows, stuffed animals, or couches that have recently been in contact with a lice-infested person
- Carefully vacuum floors and any furniture that have been in contact with a lice-infested person
- Reducing your number of sex partners can help reduce the risk of getting pubic lice
Frequently inspecting your child’s head can help identify a lice infestation early, and reduce the chance of the lice spreading to others in the household, school, or yourself.
Children should be educated about the importance of not sharing particular items or engaging in certain activities that involve head-to-head contact, which may lessen the chance of a lice outbreak at school, in a community, camp, or care center.
Maintaining healthy and clean personal hygiene and bathing daily, in addition to freshly laundering sheets and clothing, can help reduce the spread of body (clothes) lice. Using clean combs, brushes, and other personal items can help kill lice and prevent their spread.
Treatment of Lice
A lice infestation will not go away without proper care and treatment. Treatment for lice should be started immediately upon observation of lice or lice eggs. Because lice can spread quickly and easily, family members and close relations of patients with lice should be examined immediately.
Depending on the type of lice you contract, there are different methods to treat an infestation. Both over-the-counter and prescription medication options are available for lice treatment. There are many common medical creams, lotions, and shampoos that can be used to kill these parasitic lice.
Head lice and pubic lice can be treated by:
- Prescription medications, lotions, creams, or shampoos applied to the affected area – Benzyl alcohol 5% (Ulesfia), Malathoin lotion (Ovide), ivermectin (Sklice, Stromectol), permethrin 5% (Elimite), spinosad (Natroba)
- Over-the-counter creams, lotions, or shampoos applied to the affected area – Permethrin creme rinse 1% (Nix,) shampoos containing pyrethrins, shampoos containing piperonyl butoxide (Rid)
- Eye ointments for lice that settle on the eyelashes – fluorescein eye drops
- Using a fine-toothed comb to remove lice and their eggs
- Lice eggs (nits) can be killed by sitting under a hot hair dryer for at least 30 minutes – however, this does not kill grown lice
First-line treatment for these types of lice is Permethrin, which kills both lice and nits, and continues to work for several days after treatment.
In some countries, lice have become resistant to medicated creams lotions, and shampoos. Stronger medications are available with a prescription. In Britain, where this has been observed, the use of fine-toothed combs and hair conditioner helped get rid of lice.
Another possible treatment for lice, particularly head lice, is shaving your head. If you choose to do this, put shaved hair into a sealed bag to prevent further spread of lice. This drastic measure, though effective in removing lice from the body, is not necessary if you seek alternative treatment options.
Typically, no medications are needed to treat body lice, as they usually settle into clothing, linens, and bedsheets. Body lice treatment includes:
- Washing clothing in hot water – 130 degrees F (54.4 degrees C) for at least 5 minutes
- Showering the body
- Bathing daily
- Wearing clean, fresh clothes
Items that cannot be washed should be placed in an airtight bag for 2 weeks in order to kill the lice.
After lice treatment has been applied, patients may still experience itchiness due to a possible allergic reaction from lice bites. For relief from these symptoms, try:
- Corticosteroid (cortisone) creams (over-the-counter if mild, prescription if more serious)
- Calamine lotion
- Antihistamine medications (Benadryl) – do not give to children before consulting with a medical provider
Other patients have treated and found relief from lice by using other, non-scientifically proven for safety and efficacy, means. Such treatments include:
- Petroleum jelly to smother lice
- Olive oil to smother lice
When Should I Call a Doctor?
If you have contracted lice or are concerned about the possibility of a lice infestation, speak with a medical provider or pharmacist – they can help answer questions, provide advice, and give recommendations for further care.
Most cases of lice are not serious and many patients do not need to seek further medical care. Consider consulting with a medical provider if:
- You need help determining if you or your child has been infected
- Over-the-counter lice treatments do not appear to be working – do not use a product more than two times within a week without consulting a medical provider
- Symptoms, such as itchiness, are getting worse
- You are pregnant or nursing – do not use any anti-lice shampoo until speaking with a medical provider
- You develop an infection from scratching – redness, swelling, pain, and tenderness in the affected area
- You develop skin abrasions from scratching
- You have become re-infected with lice from another infected person
- You experience fever, chills, nausea, or vomiting
Consult a doctor before giving a child an antihistamine, supplying cream to a child 2 years of age or younger, or applying cream to the rectal or vaginal area of children younger than 12 years old.
Emergency Warning Signs
You should speak with a medical provider immediately if you or your child are experiencing possible allergic reactions to lice bites – with symptoms such as swelling of the lips or tongue and difficulty breathing.