Human lice infestations, a common health concern, involve three primary types: head lice (Pediculus humanus capitus), body lice (Pediculus humanus humanus), and pubic or crab lice (Pthirus pubis). These parasites cause significant discomfort due to their bites, often leading to secondary bacterial infections from scratching.

The complexity of louse-borne diseases necessitates the use of technical terms, explained in the glossary. Of the three, only the body louse is known to be a vector of disease, transmitting three different bacterial infections in humans. These lice feed on blood, injecting saliva that triggers an inflammatory response, causing itching, a common symptom of infestation. Close inspection often reveals the presence of active lice on the body or in clothing.

Body lice lay eggs in clothing, cementing them to fibers. Adult and immature lice hide in the seams and folds of clothing worn for extended periods, moving onto the host to feed. The life cycle spans 9-10 days from egg to adult, but may extend to 2-4 weeks if clothing is regularly changed.

Pubic lice, commonly referred to as “crabs,” and scabies (itch mites) are tiny insects living on the skin. They are often spread sexually but can also be contracted through shared bed linen, clothes, or towels. They typically infest hairy parts of the body, especially around the groin and underarms.

Body lice, virtually identical in appearance to head lice, can be distinguished by their location on the body. Head lice are primarily found on the scalp, while body lice may be present on both body and clothing. Their bites cause intense itching and pink papules, with large infestations leading to crusty rashes and black spots from their fecal pellets. These lice require daily feeding; without it, they quickly starve.

Transfer of head lice may occur through the use of infested combs, brushes, or contact with upholstered furniture or pillows recently used by an infested person. While body and head lice are similar in appearance, their behaviors differ significantly, with body lice preferring to reside in clothing, only crawling onto the body to feed.

For more detailed information, visit Penn State Extension, Purdue Public Health and Medical Entomology, UC Davis Human Skin Parasites & Delusional Parasitosis, Brown University Health Promotion, NC State Extension Publications, and University of Kentucky for more information.