Head Lice

Three species of lice (small, wingless insects) infest hu-mans—Pediculus humanus capitis (head lice), Pediculus humanus corpus (body lice) and Phthirus pubis (pubic lice). Many treatments exist, and patients need to ensure removal of the lice from hair as well as clothing.

Lice live and reproduce only on humans, transmitted by person-to-person contact or clothing, as human lice can survive on fabric for 10 days. Lice cycle through [Page 781]three stages—egg, nymph, and adult. Eggs are deposited on the hair shaft, providing warmth for incubation. The baby louse (nymph) hatches, leaving behind nits (casts of the empty egg)—tiny, yellow/white ovals, firmly cemented to the hair shaft. Visualization of the louse or detection of eggs within five millimeters of scalp permits diagnosis. Nits seen further along the shaft indicate prior infestation and may not need treatment.

Head lice do not transmit disease, only itching. Lice require several blood meals daily and have special mouthpieces for this purpose. Saliva is injected into the feeding site, causing sensitization to foreign antigen, eventually causing itching with repeated bites. Delousing options include chemical treatments with Federal Drug Administration (FDA) approved over-the-counter preparations containing permethrin or pyrethrins, to manual removal. Medications do not kill unhatched embryos; hence, repeat administration must be done after a week to kill newly hatched nymphs. Fine-toothed combs will remove eggs, and hair must be combed daily until there are no further signs of infestation. Vinegar will loosen eggs from the hair shaft, permitting easier removal.

All contacts of the infected individual must be treated simultaneously prevent reinfestation. Bedding and clothes must be washed on the hottest setting. Items unable to be washed should be double-bagged in closed dark trash bags, set aside for three days, then washed. Dry cleaning and ironing will kill lice and eggs. Hair implements should be soaked in a weak bleach solution or rubbing alcohol for one hour. Carpets must be vacuumed and other fabrics treated with insecticides. This entire process must be repeated in five to seven days to prevent reinfestation with newly hatched nymphs.