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Pediculosis (Lice)

Key Points

  • Pediculosis, or louse infestation, is a common clinical issue that is of limited morbidity but significant public health concern, especially in school-age children.
  • Humans may be parasitized by three louse types: body lice, head lice, and pubic lice.
  • Because lice live on clothing or hair (scalp, genital hair, or eyelashes), the primary therapeutic strategy is to identify the type of lice and to completely remove or treat the existing lice and eggs.

Introduction

Humans may be parasitized by three louse types: body lice, head lice, and pubic lice. Body lice live in the patient’s clothing, not on the body. They are often found along seam lines of clothing apparel and can also be found in bedding. Head and pubic lice are found on the hair of the scalp and genital area, respectively. Pubic lice may also infest the eyelashes. Though not considered a serious threat to human health, louse infestation is contagious and can become a public health concern, especially when infestations affect school-age children, their caretakers, and household members. It is important to note that the patterns of treatment-resistance especially to over-the-counter products have emerged, and thus the therapeutic strategies have shifted in recent years.

There is limited morbidity associated with lice. The primary concern is a hypersensitivity reaction to components of the louse saliva, which results in pruritus 4-6 weeks following the onset of the infestation. Notably, severe pruritus may result in excoriations with secondary skin infections such as impetigo. Human body (but not head) lice are rarely associated with the spread of relapsing fever (Borrelia recurrentis), epidemic typhus (Rickettsia prowazekii), and trench fever (Bartonella quintana).