Nix, or 1 percent permethrin, is an over-the-counter topical lotion that kills hatched lice but not their unhatched eggs, according to the Centers For Disease Control and Prevention. It continues to work for several days after application, killing newly hatched lice. In many cases, a second treatment is necessary after nine days in order to kill any additional hatched lice before they are able to lay eggs.Continue Reading
The product box contains directions regarding how long to keep the lotion on the hair during treatment and how to wash it out. Conditioning the hair immediately before treatment or shampooing within one to two days after treatment can reduce the effectiveness of the medicine, advises the CDC. Within eight to 12 hours of treatment, the lice should be dead or moving more slowly; if they are alive and active, the treatment may have been ineffective. Combing the hair with a special nit comb two to three days after treatment is helpful in preventing reinfestation. For two to three weeks, the affected person should have someone carefully check their scalp for signs of remaining lice or nits.
Additional steps to kill lice or unhatched eggs that may be present in the living areas of the infested person include washing and drying the person's clothing and bed linens, and vacuuming furniture or sealing unwashable items in a plastic bag for two weeks. However, since lice cannot live for very long when they are off the scalp and unable to feed, these steps are not always necessary, states the CDC.Learn more about Medications & Vitamins