Ultimate Guide on the Diagnosis and Treatment of Lice

Like most parents, I was horrified when I discovered my daughter had head lice. But, as a pediatrician, I knew there was no real cause for alarm. The head louse, or pediculus humanus capitis, is pesky, and maybe even a little yucky, but essentially harmless. These tiny six-legged insects, which cling to the scalp and live on small amounts of blood, do not spread disease. They don’t jump or fly. And they don’t live more than a day or so once they leave your scalp. So you can only spread them through head-to-head contact, by using an infected person’s hat or hairbrush, or by resting your head on a pillow or carpet where the infested person has rested his or hers.

Head lice are also not a reflection on your family’s hygiene. Parents often worry that a lice infestation means their child or their home is dirty, but this is not true. Anyone who comes in head-to-head contact with someone with lice is at risk, though infestations are most common among children ages 3 to 11, especially girls (perhaps because of their long hair). They are least common among African Americans, perhaps because lice are best adapted to cling to certain types of hair shafts.

It’s also important to know that lice infestations can be easily misdiagnosed. People frequently confuse the nits – the tiny white eggs laid by lice that attach to the hair shaft near the scalp – with dandruff and other debris. Unlike dandruff, though, nits are difficult to dislodge and usually show up brown and pointed against a white background. But even spotting nits does not mean you have an active infestation. Nits found more than a quarter-inch away from the scalp have most likely already hatched, and, in the absence of live lice, should not be treated.

So how are lice diagnosed?

Most lice infestations don’t cause immediate symptoms, though children may complain of feeling things crawling around or tickling their heads. (It sure makes me scratch my head as I write this.) If your child does have a reaction – usually an itchy or irritated scalp – it will most likely occur four to six weeks after infestation.

If you suspect lice, wet your child’s hair and go through it carefully with a fine-toothed comb. Use a magnifying glass, if necessary, to scan for live, moving insects, usually tan to grayish-white and about the size of a sesame seed. Have a bowl of hot, soapy water ready to drown them as you remove them with the comb.

Lice cling to the scalp and neck, especially around the ears or hairline. Nits close to the scalp are the ones most likely to hatch. One way to loosen them is by wetting the hair with a solution of half water, half vinegar (unfiltered apple cider vinegar is a good choice).

If you do find live lice, other family members and children at school or daycare who may have been exposed should also be checked. But don’t worry about pets. Lice can’t live on animals because they need human blood to survive.

Treating Head Lice

Standard treatment for head lice has long been the use of over-the-counter products, including shampoos and lotions that contain the pesticides permethrin or malathion. (Products with pyrethrins are also used, but can cause reactions in people with chrysanthemum allergies.) Be sure to follow the instructions carefully, and never use more than the recommended amounts.

A few important points to remember: Sometimes these treatments must be repeated to eliminate any surviving nits that have hatched since the initial treatment. Also, some lice have become resistant to these chemicals. Pesticides should never be used on infants.

Because many parents don’t want to use pesticides, I recommend removing lice and viable nits by hand, with the same fine-toothed comb you use for diagnosing them. Each infested member of the family should be treated at the same time, and you should do the wet combing every three to four days for three weeks after the last live louse is seen.

Because lice cannot survive more than 48 hours away from the scalp, you don’t need to do a lot of house cleaning. But you should wash bedding and clothing used by the affected child in very hot water, at least 130 degrees Fahrenheit, and dry on high for 20 minutes. Pillows can also go into a hot dryer. Combs and brushes can be soaked for an hour in rubbing alcohol. It isn’t necessary to clean stuffed animals, but if you are concerned, you can leave them in airtight bags for two weeks.

Some schools still routinely send children home if they show any signs of a possible lice infestation, including nits, but we now know that is not necessary. Most nits do not indicate an active infection, and we know that spreading lice can be prevented by simply avoiding head-to-head contact. Along these lines, it’s always good practice to discourage your kids from sharing hairbrushes and combs, hats or sports helmets and hair ribbons or barrettes.

A visit to your doctor is warranted only if you’ve treated the problem at home and the lice keep coming back, or if your child has been scratching so much that they’ve created sores that have become infected.

As a pediatrician, I tell parents not to worry about lice, but I do understand their discomfort. When my daughter had lice, I wanted to scrub my house from top to bottom. But as a physician, I told myself what I tell my patients: This is normal. It’s manageable. I don’t need to fumigate. And everything is going to be okay.

To find out more about preventing and treating head lice, visit the Centers for Disease Control and Prevention’s website: