- Research suggests a large number of head lice in the U.S. have genes that could make them resistant to over-the-counter treatments
- Experts still recommend these over-the-counter products, as well as combing, as the first line of defense against head lice
- Companies that offer lice removal services, including combing and hand removal, are doing a "booming" business
(CNN)Head lice are a lousy part of the school year or summer vacation for an estimated 6 to 12 million children in the United States every year. Infestations can lead to itchy scalp, irritability and poor sleep.