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Column originally published Nov 29, 2016

Head Lice

Question: Our ten-year-old daughter’s best friend was recently diagnosed with head lice. They have sleepovers almost every weekend at each other’s home. I checked our daughter and found some nits that resembled the pictures on internet. She has no symptom at all. I wonder whether I should treat her. I didn’t tell her teacher yet. We also have an eight-month old baby; I didn’t find anything in his hair. Please give us some advice.


Head lice infestation is very common in children. It is not a reflection of a person’s hygiene, although many schools have nit-free policy which is not necessary. Finding nits on the hair doesn’t imply active infestation.

Head lice are tiny insects measuring 2-4 mm long. They have no wings, but can run very fast, about 23 cm (almost 9 inches) a minute! They spread from person to person through close head contact. That is why they spread easily among children. They live on their scalp and feed every 3 to six hours by sucking blood and injecting their saliva simultaneously. Over time, some children become sensitive to the saliva and develop itchiness. Others have no symptom at all.

Adult females lay eggs that are glued to the hair close to the scalp; these are called nits. Young insects hatch after 10 days; it takes another 10-15 days before they become mature lice. As the hair grows, the nits are moved away from the scalp. Most nits that people find are actually empty shells. In order to diagnose head lice infestation, you need to use a fine-tooth lice comb and look for live lice.

You likely worry about head lice spreading throughout your home. This is quite unlikely; head lice need to stay close to the scalp for moisture and heat, as well as getting frequent meals. They die within 1 to two days if they come off the scalp. You can wash pillowcases and hats in washer and dryer using hot cycles. Brushes and other items that cannot be washed should be sealed in a plastic bag for two weeks. This will kill all lice and eggs completely. There is no need to do any further house cleaning.

There are many lotions and creams that you can use to treat head lice. Pyrethrins are chemicals extracted from chrysanthemum flowers; permethrin is a related synthetic chemical. Both can kill the lice but not the eggs. Therefore, a second application after 9 to 10 days is necessary to kill the newly hatched insects before they can lay further eggs.

Resultz is a solution that dissolves the outer shell of lice, exposes their bodies to air and kills them by dehydration. Another new product called NYDA that contains 92% silicone oil flows into the breathing system of lice, young insects and egg embryos, suffocates them.

All of these treatments are safe, and you have to follow the instructions carefully and completely. Otherwise, it can lead to treatment failure. Some are not recommended for young children; many require a second treatment after certain number of days. You should consult with your pharmacist or physician if you are uncertain which one to choose.

If you go on the internet, there are websites that suggest the use of household items like mayonnaise or olive oil. They are not effective. Others suggest repeated combing of wet hair with a fine nit comb every few days; research has shown that this has a high failure rate. They are not worth your time and effort.

If you find live lice on your daughter’s scalp, you should use one of the treatments that I have mentioned here. You should remove nits still sticking to her hair to prevent others from thinking that she is infectious. After that, relax.