How many head lice are usually found on an infested person? 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.
Infested children usually carry fewer than 20 mature head lice (more commonly less than 10), each of which, if untreated, live for three to four weeks (5–7). Head lice stay close to the scalp for food, warmth, shelter and moisture (6,7).
Adult female head lice are usually larger than males and can lay about six eggs each day.
How soon do symptoms appear after exposure? Some people may not have symptoms, particularly with the first infestation or when the infestation is light. It may take 4-6 weeks for itching to appear the first time a person has head lice.
Can someone have nits but no lice? It may be possible to have nits but no lice. If a person cannot find any nymphs or adult lice in the scalp and the nits are more than a quarter of an inch from the scalp, these may be dead and from an old infestation.
Not everyone feels lice moving around on their scalp, but some people do. Dr. Garcia says that most of her patients say they “don't feel anything,” but others may get a creepy, tickling sensation as lice move around their head.
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. Life cycle image and information courtesy of DPDx.
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.
After Treating with Lice Medicine
Use the nit comb to remove dead lice and nits. If some are still present but moving slowly, do not shampoo again. If lice are still active and no dead lice are found, call your health care provider. These lice may be resistant to the medicine.
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.
Heat Method:
There are recent studies that show that treatment of lice with heat can be quite effective in killing head lice. Products such as Lousebuster are very effective but even a home hairdryer can successfully treat lice.
In the United States, infestation with head lice (Pediculus humanus capitis) is most common among preschool- and elementary school-age children and their household members and caretakers.
Adult lice are no bigger than a sesame seed and are grayish-white or tan. Nymphs are smaller and become adult lice about 1–2 weeks after they hatch.
It's essential to wash all bedding after a head lice treatment. The heat from a hot water cycle will ensure that no surviving lice can find a host again.
Because the active ingredients have remained the same all these years, new generations of head lice have become immune to them. Once lice become immune, the product no longer works. Scientists call this resistance.
If the freezer is 5°F or lower, all lice and eggs should be dead within 10 hours. Also, keep items and areas off-limits to people for 48 hours to limit exposure to any live lice.
Nits that are attached more than ¼ inch from the base of the hair shaft are almost always non-viable (hatched or dead). Head lice and nits can be visible with the naked eye, although use of a magnifying lens may be necessary to find crawling lice or to identify a developing nymph inside a viable nit.
New eggs are attached to the hair shaft very close to the scalp. Eggs that still contain a louse embryo are brownish in color, while the empty egg shells are white to grey.
The only way to be sure someone has head lice is by finding live lice. You can do this by combing their hair with a special fine-toothed comb (detection comb). You can buy these online or at pharmacies.
Coconut, tea tree oil, lavender, eucalyptus, rosemary, lemon grass, and peppermint are scents popularly believed to repel lice. Using any coconut scented shampoo and conditioner is an easy way to increase your defense.
Although sometimes more tedious than chemical methods, mechanical lice treatment methods are far more effective at destroying lice for good. Lice may develop resistances to certain chemicals; however, they will never be able to resist being squished, zapped, smothered, or manually removed by the human hand.
You may be able to see the lice, but they're often hard to spot because they're small, avoid light and move quickly. Lice eggs (nits) on hair shafts. Nits stick to hair shafts and may be hard to see because they're very tiny. They're easiest to spot around the ears and the hairline of the neck.