Lice are tiny parasitic insects that feed on blood and are easily spread from person-to-person. Lice infestations are very common, with an estimated six to 12 million children between three and 11 years of age getting head lice each year, according to CDC estimates. 

There are different kinds of lice, but the most common are head lice, infestations of which are particularly common among school children. Body lice are more common in people with poor hygiene or who are not able to bathe or launder clothes. Pubic lice, also called crabs, are found in the hair around the pubic area and occasionally in other body hair and are usually transmitted during sexual contact.  

Symptoms of a lice infestation are intense itching on the scalp or affected area, a tickling feeling as hair moves, the appearance of lice on the scalp or clothes, lice eggs on hair shafts, and small red bumps on the scalp, neck, and shoulders. 

Treatment of lice usually involves over-the-counter medicated shampoo to kill the lice and eggs. In cases of severe infestation, or where there products do not work, doctors may decide to prescribe a stronger shampoo or mediation. Drug classes commonly used to treat lice include ectoparasiticides, including scabicides and antinematodal agents.