Lice belong to a group of flightless, blood-feeding insects that are externally parasitic on mammals and birds, meaning that they live and feed on the surface of the host body. Three main species are problematic for people, the head louse, body louse, and pubic louse (also known as crabs).
Smaller than you would expect, adult head and body lice are no more than 1/8 inch (3mm) long or the size of a sesame seed. They are pale white to gray, wingless but with 6 legs, and may have a red spot in the abdomen if recently fed.
Head and body lice are visually identical, but differ in behavior and ecology. Body lice likely evolved from head lice about 100,000 years ago adapting to laying eggs and living in clothing, a human advancement dating to roughly the same time period.
Pubic lice, are smaller and have a rounder shape and larger tarsi (toes). Juvenile lice of all three species look like smaller versions of the adults.
Eggs, also called nits, are laid and cemented in place on the hair shaft close to the skin, or in the case of body lice, the seams of clothing close to the skin.
If you have found an insect you can’t identify, consider bringing it to your local Cornell Cooperative Extension office for identification.
Human parasitic lice have sucking mouthparts used to pierce the skin in search of blood. Like mosquitoes, lice release saliva to prevent clotting and this causes itching and irritation through an allergic reaction. Lice also move around, causing a tickling feeling. Both sensations can be alarming to some and cause poor sleep that can lead to other ailments. Scratching causes sores that can become infected.
While head lice stay in the hair of the human head, body and pubic lice feed on parts of the body covered by clothing. The armpits, waist, groin and upper thighs are most susceptible to body louse bites. Body lice are often found in communities after natural disasters, communities in poverty, and in war-torn countries. Body lice can transmit serious disease-causing organisms, including epidemic typhus (Rickettsia sp.), trench fever (Bartonella quintana, related to cat-scratch fever) and relapsing fever (Borrelia sp., similar to Lyme disease). Pubic lice are often found in the genital region on pubic hair, but may also be found on body hair, including arms, legs, the beard, eyebrows and even eyelashes. Though rare, pubic lice can even be found in the eyelashes of children and this may be a sign of sexual abuse or neglect.
Head and pubic lice do not spread disease-causing organisms.
The condition of being infested with lice of any kind is called pediculosis. Lice that plague humans are delicate and cannot live any part of their life stage (egg, nymph or adult) off their host for more than 48 hours due to the need for warmth and humidity. Head lice are extremely contagious between people; they are not a sign of poor hygiene or socio-economic status.
Head lice are commonly shared among school-age children because they tend to play together in close contact. Adults who care for and live with children who have head lice often become infested as well. Regular shampooing does not prevent or eliminate head lice.
Body lice are generally uncommon in America, but they can be found in places where hygiene is poor and people are vulnerable, such as among the homeless and residents of nursing homes. Again, body lice are transmitted person to person through physical contact.
Pubic lice are mostly transmitted through sexual activity, but can be spread to adults or children in contaminated bedding, towels, or clothing.
Human parasites are considered medical issues, not pest management issues. To learn more about available treatments we direct you to the lice treatment pages of the Mayo Clinic and the CDC’s pages on treatment of head lice, body lice and pubic lice. Aside from insect-killing shampoos and creams, head lice can be managed using a lice comb. You can learn more about the wet-combing technique from this educational video. Many communities have people experienced in wet-combing lice-removal and offer their services for a fee, which can be very effective and pesticide-free.
There are instances when lice end up in the human environment and need to be quickly dispatched. In a home, school or other space occupied by people, there is never a reason to use pesticides to kill lice that have fallen off a person. Few, if any, pesticides are labeled for this use. Lice that fall off a person indoors cannot move far and will die within 36-48 hours. Cleaning is the best option. Vacuum areas suspected of contamination. Wash and dry (or just dry), bedding linens, clothing, towels, and any other fabric items to kill lice. Tumble drying on high heat for 15-20 minutes is fast and effective for items that fit inside a dryer.
There are also preventative measures to reduce the risk of getting lice. Head lice often spread quickly through schools and child care facilities. Instruct kids to avoid touching their heads or sharing brushes, hair clips, hats and scarves. Inspect your child’s hair periodically, especially if lice have been found in the classroom or school. Products are available that claim to “prevent” lice, but those claims are dubious and the products are untested for repellency to lice.