To treat head lice effectively, start with an over-the-counter medicated shampoo containing Permethrin (1%) or Pyrethrins. Apply it according to the package instructions, leave it on for the specified time, and rinse. Crucially, use a fine-toothed nit comb on wet hair to remove dead lice and eggs (nits). Because these treatments do not always kill unhatched eggs, you must repeat the treatment in 7 to 9 days to kill newly hatched lice. Additionally, wash recently used bedding and clothing in hot water. If over-the-counter treatments fail, consult a doctor for prescription options like Spinosad or Ivermectin.