Primary Care in Rochester and Kasson

Don't sweat the small (crawly) things

9/1/2022 by Julie L. Hanson, M.D.


You just received a message from your child's school: "Your child has been exposed to head lice." As you immediately feel your scalp start to crawl and itch, you ask yourself: "What are head lice? How do they spread? What do I do next?"

Head lice can be stressful and bothersome, but they do not spread diseases or cause significant harm. 

Your Primary Care in Rochester and Kasson team has the answers to common questions to help you manage this itchy nuisance:

What are head lice?

Head lice are tiny wingless insects that are about the size of a sesame seed. A single insect is called a louse. Once fully mature, an adult female louse can lay up to 10 eggs per day. These eggs are firmly attached to hair near the scalp.

The eggs and their surrounding shells are called nits. Most nits are yellow or white, but some can blend in with a person's hair color and may be more difficult to see. Once the eggs hatch, the empty shell casings stay in place on the hair shaft. It typically takes around three weeks for an egg to hatch, and for a louse to reach adulthood and begin to make eggs of their own. 

Head lice can typically only survive for one to two days away from the scalp. They feed by sucking tiny amounts of blood from the scalp. Head lice inject a small amount of substance into the scalp to make it easier for them to feed. The scalp reacts to this substance, and this causes the itching associated with head lice. 

Who gets head lice?

Head lice infestation is a common issue that most frequently affects children in preschool and elementary school. Head lice are found worldwide. They will attach to anyone's hair, regardless of how clean or dirty it is. 

How do head lice spread?

Head lice cannot jump or fly. They can only crawl. Transmission primarily occurs through prolonged head-to-head contact. Contact with the combs, brushes or hats of an infested person provides a much smaller chance of spreading head lice. Dogs, cats and other animals do not spread head lice. 

How do you know if your child has head lice? 

Monitoring your child's hair regularly helps identify lice before they multiply and potentially spread to others. To confirm a head lice infestation, it is best to find live lice on the scalp. 

How do you check for head lice?

  • Have your child sit in a brightly lit room. Part their hair in sections. Look for crawling lice or nits one section at a time. 
  • Live lice are small and move quickly to avoid light. Using a fine-tooth comb may help identify live lice. 
  • Finding nits attached to a hair shaft within about a quarter-inch from the scalp suggests the likelihood of an active lice infestation. Nits attached further down the hair shaft usually are already hatched, or they are dead lice. This may suggest an old infestation that need not be treated. 
  • Nits are typically best seen on the hair behind the ears and near the hairline on the back of the neck.

How are head lice treated?

Head lice should only be treated if you're certain that your child has living lice on the scalp. Check with your clinician before beginning head lice treatment, particularly if your child is 2 years old or younger. 

You can purchase many head lice medications over the counter. Home remedies, such as essential oils, petroleum jelly, mayonnaise, butter and olive oil have not been proven to be effective. Always avoid using harmful substances, like gasoline or kerosene, and never place a plastic bag on your child's head. 

Here are some additional tips for using lice medications safely and effectively:

  • An adult should apply lice treatments according to the package directions. 
  • Do not rinse the medication off in a shower or bath, as the medication can get on other areas of skin. Instead, place your child's head over a sink and rinse off the medication with warm — not hot — water. 
  • Do not use hair conditioner prior to applying the medication, as this may make the medication less effective. 
  • After treatment with a medication, use a fine-toothed comb to remove nits and lice. 
  • You may need to repeat lice treatment after seven to 10 days, or as directed on the medication package if live lice are still seen after treatment. 
  • Check all close contacts and household members for lice and treat if lice are identified. It may help to treat family members who have shared a bed with your child. 
  • It also may be beneficial to wash clothing, hats, towels and bedding that have recently come into contact with your child's head. Washing in hot water and drying with high heat should kill any lice on these objects. Seal items that cannot be washed, like stuffed animals, in a plastic bag for two weeks. 
  • Do not spray pesticides in your house. Pesticides can harm your family's health and are not necessary to treat lice in your home. 

If you do not notice an improvement in your child's symptoms after using the medication, reach out to your child's primary care clinician to discuss other treatment strategies. 

Julie L. Hanson, M.D., is a pediatrician in Primary Care in Rochester and Kasson's Division of Community Pediatric and Adolescent Medicine. She practices at Mayo Family Clinic Northwest in Rochester. Her areas of interest include refugee and global health, newborn care and complex care management.