Lice are ectoparasites that feed on human blood after piercing the skin and injecting their saliva. Most infestations involve 10-20 adults. The adult female louse lays 3-10 eggs, called nits, per day at the base of the hair shaft. Nits hatch in 8 days if they are kept near body temperature, and they mature in another 8-9 days. A mature female louse lays 3-6 eggs, or nits, per day.
Nits are white and they are less than one millimeter long.
Hair length and personal cleanliness are not factors in infestation rates. Lice infestation more often causes social embarrassment and isolation of the patient, rather than medical complications. All races are affected. Reported incidence in African Americans in the United States is relatively less than in Caucasians. All age groups are affected.