When using a head lice medication::
• Apply according to instructions. If the person has long hair, a second bottle may be needed. Pay attention to instructions regarding how long the medication should be left on the hair and how it should be washed out.
• Have the person put on clean clothing after treatment.
• If a few live lice are found 8 to 12 hours after treatment, but are moving more slowly, don’t re-treat. The medicine may take longer to kill all the lice. Comb lice out of the hair using a fine-toothed nit comb.
• If, after 8 to 12 hours of treatment, no dead lice are found and lice seem as active as before, the medicine may not be working. Don’t re-treat until speaking with your doctor.
• After each treatment, check the hair and comb with a nit comb to remove nits and lice every 2 to 3 days to reduce the chance of self-reinfestation.
• Retreatment is meant to kill any surviving hatched lice before they produce new eggs. Ask your doctor if you have questions about retreatment.
Source: U.S. Centers for Disease Control and Prevention