What Are Head Lice?

Head lice (Pediculus humanus capitis) are tiny, wingless, parasitic insects that can infest the scalp. Head lice survive and thrive solely on human blood, so once they're separated from their human host, they starve and die within hours.

Read on to learn more about the signs and symptoms of head lice, how they spread, and how to get rid of them.

The most common signs of head lice are:

Instead, “direct head-to-head contact is how we transfer lice,” says Richard J. Pollack, PhD, president and chief scientific officer of Identify US, a company that consults on a wide range of pest management challenges, and a former senior environmental public health officer and researcher at the Harvard School of Public Health in Boston.

With that, here are the risk factors for head lice:

Lice are very small and move quickly, so begin by parting the hair into small sections and using a magnifying glass, as well as a special fine-toothed metal comb called a nit comb.

“If you find a crawling bug on the scalp hair and it looks consistent with the images of head lice, then your lice conclusion is likely correct,” says Pollack.

“There are a lot of misdiagnoses at school head checks,” says Pollack. “Parents should carefully consider the evidence before starting treatment.”

It's only recommended that you proceed with head lice treatment if an active infestation of head lice is confirmed. Meaning: The lice need to be alive and crawling, or the lice eggs need to be viable, to warrant treatment. Still, it may be prudent to go ahead and treat those who share the same bed with an actively infected person.

Medication Options

• Nonprescription Lice Shampoo and Cream Every over-the-counter (OTC) treatment of head lice has been approved by the U.S. Food and Drug Administration (FDA) and contains either pyrethrins (Rid or Triple X) or permethrin (Nix). Both are effective and are considered the first line of treatment. The former can be used on children ages 2 and older, while the latter can be used on children as young as 2 months. Both only kill live lice, not nits.

  [9]

  After an initial at-home treatment, check hair to see if lice appear less active after 8 to 12 hours. If you don't notice a difference, refrain from re-treating. Instead, check with your doctor to see if another product may be needed.

  [10]

   If, after that time frame, you do notice a slowdown, it's still recommended that you re-treat within seven to nine days to kill any lice that have hatched after the first round. Two treatments usually get rid of the lice. (Combing hair for two to three weeks also helps.)
• Prescription Shampoos and Lotions If an at-home product doesn't knock out the infestation, talk to your doctor or dermatologist. They can prescribe a stronger lice treatment, like prescription permethrin. Lindane, a prescription lotion or shampoo, is less effective than prescription-strength permethrin and, because of the possible toxic side effects, is not recommended for children younger than 2, pregnant or lactating women, or those with a seizure disorder. While prescription malathion is very effective at killing both head lice and lice eggs, it's not considered a first-line treatment because it needs to remain on hair for 8 to 12 hours to work.

  [11]

• Other Prescription Options Benzyl alcohol lotion (Ulesfia), ivermectin (Stromectol) lotion, and spinosad topical suspension are additional prescription options.

  [11]

• Oral Prescription Medication When other treatments fail, oral ivermectin may be an option. While it effectively treats a head lice infestation with two doses eight days apart, side effects may include nausea and vomiting. (Children must weigh at least 33 pounds to take this medication.)

  [12]

Manual Treatment

Complementary Therapies

Heat A device called AirAllé uses a 30-minute blast of hot air to kill lice. It has been shown to be an effective method, knocking out nearly all lice eggs and 80 percent of live lice after one treatment. This special machine is only found at professional lice treatment clinics. (A regular blow-dryer does not work in the same way and should not be used as treatment, since blow-dryers can cause lice to become airborne and can also burn the scalp if used incorrectly.

In addition to treatment, you can take steps to help prevent reinfestation. Even though it's highly unlikely for lice to spread through sharing belongings, such as hats, it's still a wise idea to refrain from trading hair accessories, brushes, combs, and towels — especially with an individual with a known active case of head lice. Other ways to prevent getting and spreading lice include:

• Launder items. Change and launder the infested person's pillowcases, pajamas, towels, and other items that their head was in direct contact with during the 24 to 48 hours before diagnosis. Machine-wash it all in hot, soapy water, then dry on the hot cycle for at least 20 minutes.

  [1]

• Soak brushes. Submerge the infested person's combs, brushes, barrettes, and hair bands in hot water for roughly 10 minutes.

  [3]

• Vacuum surfaces. Use a vacuum on carpets, furniture, car seats, beds, and other items that have been in contact with the head of the infested person within the previous 24 to 48 hours.

  [1]

• Seal up other items. Although it is rarely necessary, you can also place pillows and stuffed animals in a tightly sealed plastic bag for two weeks to suffocate any possible remaining nits or lice.

  [3]

• Avoid sprays. Not only is fumigating the home with pediculicide spray not needed in order to control head lice, but inhalation of fumigant sprays can be toxic.

  [1]

But there is debate about whether this theory is accurate, says Candrice R. Heath, MD, assistant professor of dermatology in the Lewis Katz School of Medicine at Temple University in Philadelphia. “It's also speculated that the use of oils and tightly coiled hair shafts may be reasons that lice occur less frequently in the hair of Black children.”

Of course, that doesn't mean that Black children don't get lice. They do. So it's important to monitor any signs, such as scalp itching, regardless of a person's race or ethnicity. It's also important to adapt lice detection and lice removal techniques based on the texture of the child's hair. For instance, head lice checks often involve using a comb with teeth that are closely spaced together. “When these standard lice combs are used on tightly coiled hair, it can be a challenge to adequately comb from the root without causing breakage or scalp pain,” says Dr. Heath. Instead, you might need to detangle the hair with a wide-toothed comb before using a lice comb. And when combing out hair during treatment, wetting and coating hair with conditioner will allow for a smoother comb-through.

• Head lice are tiny, wingless, parasitic insects that can infest the scalp; they spread primarily through head-to-head contact.
• Lice are most commonly found in young children who spend time at school and in daycare settings.
• Most cases of head lice are effectively treated with topical applications. A fine comb designed for identifying lice and their eggs is also helpful for removing them manually.
• Schools often require children with lice to stay home until the lice are gone or there are no signs of nits (eggs). This policy is not considered necessary by several leading medical organizations.