Body lice (Pediculus humanus humanus) are parasitic insects that feed on human blood. They are ectoparasites, meaning they live on the outside of the host’s body. They primarily infest clothing and bedding, moving to the skin only to take a blood meal. Understanding the appearance and location of the adults and their eggs is essential for identification and management.
Identifying the Adult Louse
The adult body louse is a small, wingless insect that measures between 2.5 to 3.5 millimeters in length, roughly the size of a sesame seed. The body is elongated and segmented, supported by three pairs of legs equipped with claw-like structures used for grasping fabric fibers.
The coloration varies, typically appearing tan or grayish-white when unfed. After consuming a blood meal, the insect’s abdomen swells and takes on a darker, reddish-brown hue. Adult body lice are most often found within the seams of clothing, particularly in tight areas like the waistline and armpits. They only crawl onto the skin briefly to feed, making them less visible on the body itself.
Appearance and Location of Nits
Body lice eggs are called nits, appearing as tiny, oval, yellow-white capsules measuring about 0.8 millimeters by 0.3 millimeters. They are firmly attached to surfaces using a strong, cement-like substance applied by the female louse, and their presence is a definitive sign of an infestation. The primary location for nits is on the fibers of clothing, especially along the seams and folds. They are rarely found attached to body hair, which helps differentiate them from other lice species. Once laid, a nit hatches into an immature louse, called a nymph, within seven to ten days.
Key Differences from Other Lice
It is important to distinguish body lice from the two other types that infest humans: head lice (Pediculus humanus capitis) and pubic lice (Pthirus pubis). Body lice are slightly larger than head lice, though they are nearly identical in overall body shape. The primary difference is locational, as head lice live and lay their eggs on the hair shafts of the scalp.
Pubic lice, often called “crabs,” are the smallest of the three and possess a broader, more crab-like body shape. They primarily infest coarse body hair, such as the pubic area, armpits, and chest hair. Identifying the location of the louse and its eggs—clothing seams for body lice versus hair for the others—is the most reliable method of differentiation.
Steps After Identification
If an infestation is confirmed by finding adult lice or nits in clothing seams, the focus shifts immediately to sanitation and hygiene. Treatment centers on removing the insects from their habitat through thorough cleaning of all potentially infested clothing, bedding, and towels.
Clothing and bedding should be washed in hot water (at least 130°F), followed by a high-heat drying cycle to kill all lice and nits. Regular bathing and changing into clean clothes are necessary to disrupt the louse life cycle. If the infestation is persistent or severe, consulting a healthcare provider is recommended for specific guidance.