Benzyl alcohol lotion, 5% has been approved by the FDA for the treatment of head lice and is considered safe and effective when used as directed. It kills lice but it is not ovicidal. A second treatment is needed 7 days after the first treatment to kill any newly hatched lice before they can produce new eggs.
Generally, if no live crawling insects are seen three weeks after the treatment, it's safe to assume that they are gone. Nits would have hatched by that time if they were alive. Nits and their shells may remain in the hair for some time but won't be viable.
Medicated lotions and sprays
Head lice should die within a day. Some lotions and sprays come with a comb to remove dead lice and eggs. Some treatments need to be repeated after a week to kill any newly hatched lice.
Many lice medicines recommend a second treatment in 9 to 10 days. This will kill any new nymphs that have hatched since the first treatment. Do not treat a person more than 2 times with the same medicine without talking to your doctor. Do not use conditioner for 10 days after any treatment.
Head lice survive less than one or two days if they fall off the scalp and cannot feed. Head lice eggs (nits) cannot hatch and usually die within a week if they do not remain under ideal conditions of heat and humidity similar to those found close to the human scalp.
Adult lice can live up to 30 days on a person's head. To live, adult lice need to feed on blood several times daily. Without blood meals, the louse will die within 1 to 2 days off the host.
Comb dead and any remaining live lice out of the hair using a fine–toothed nit comb. If, after 8–12 hours of treatment, no dead lice are found and lice seem as active as before, the medicine may not be working.
It's possible that the nits are leftover from a previous infestation and are no longer viable, which means they are dead and won't hatch. It's difficult to tell the difference, so you should still treat any nits you find, even if there are no lice.
Infestation timeline
So if you look on the scalp and see no visible adult lice and several small nits, it's likely that you've caught lice in the earlier stages and had them for less than 2 weeks. Nits and nymphs: 1.5 to 2 weeks. If you see nits and small, moving lice, you've likely had lice for 1.5 to 2 weeks.
Typically, 10–15 head lice are found. The number of lice often depends on personal hygiene, for example, how often the person bathes, shampoos, or changes and washes his/her clothing.
Lice can be hard to get rid of. If you still have lice 2 weeks after you started treatment, let your doctor know. Your doctor may want to try a different medication or repeat treatment in case any nits were left behind and hatched after treatment.
Repeat treatment every day or every other day for 2 weeks. Some lice eggs (nits) survive head lice treatments. The only way to be sure that lice won't come back is to pick out all nits. Nits left on the hair can hatch and cause a new case of head lice.
Adults are not immune to head lice. In fact, if you have any close contact with children or even parents of children you can be at risk of catching them if they have them. Lice transfer primarily through head to head contact, so you would have to get close to the other person.
The oval-shaped eggs often look yellow or white but may be the same color as your hair. They are found on the first 1-2 inches of hair shaft closest to the scalp (not the end) and are hard to remove. You may confuse them with dandruff or flakes from hairspray build-up. Head lice nits usually hatch in 8 to 9 days.
Nits are often confused with other things found in the hair such as dandruff, hair spray droplets, and dirt particles. If no live nymphs or adult lice are seen, and the only nits found are more than ¼-inch from the scalp, the infestation is probably old and no longer active and does not need to be treated.
Adult lice can't live longer than 24 hours or so on nonhuman surfaces like carpets, hardwood floors, clothing, furniture, sports helmets, headphones, or hair accessories. However, if you have identified lice in your home, isolate and wash those items and areas within at least 72 hours.
Children can have a few nits without actually having a case of head lice. Usually children have no more than 10 to 20 live lice. Good lighting is important when you are checking. Head lice move fast and are hard to see.
They move fast. To check for lice, look through your child's hair with a fine comb, looking in particular behind the ears or base of the neck.
Either washing done with a water temperature of at least 50 degrees C or drying is necessary to kill head lice and nits.
So, the realistic answer is “No, you can't drown lice.” The best treatment for lice is to get them picked out by a professional – Lice Geeks, for example – using the right comb. Even over-the-counter shampoos and products aren't as effective as a well-trained professional wielding the proper comb.
Vinegar contains properties that kill and get rid of nits and lice. This mixture should be applied directly to the whole scalp. Mix 1 cup of vinegar with 1 cup of warm water. Next, distribute this mixture onto the scalp and cover your hair with a hair cap.
The longer answer goes back over 800,000 years. Scientists believe head lice began to evolve on a different path than body lice about the time humans started to wear more clothing. Body lice evolved to attach to clothing fibers which are typically thicker and stronger than a human hair. Head lice stuck with the scalp.
Usually, you would have to be in head-to-head contact with a person who has lice. This can be common in schools or kindergartens, where children are often close together. Sharing combs, brushes, towels, hats, and other personal items can hasten the spread of head lice.
If you see sesame-seed-shaped objects, those are the nits and lice, which can be brown or grey and stand out against the white paper towel. “The nits may look like they have tails that stick out the back,” says Faulkner.