Head Lice: Diagnosis and Therapy

Gabriel J. Martinez-Diaz, MD; Anthony J. Mancini, MD


Dermatology Nursing 

In This Article


The diagnosis of head lice is made easily with the identification of live lice, either via inspection of the scalp or when combed from the hair after wetting it. Visual inspection for live lice without combing can be challenging, as the head louse crawls rapidly and likes to avoid light (Bacot, 1917). The identification of nits attached to hair shafts does not confirm active disease, but if they are within 1 cm of the scalp, an active infestation is more likely (AAP, 2009; British Medical Journal Publishing Group, 2009; "Getting the Bugs Out," 2009; Janniger & Kuflik, 1993; Mumcuoglu et al., 1991; Namazi, 2003; Vander Stichele et al., 2002). The diagnosis of lice can sometimes be confirmed with the use of a hand lens or microscope. Table 1 lists the differential diagnosis of nits. The ability to easily slide off debris, scales, and hair casts usually helps to distinguish most of these mimickers from true nits, which are firmly cemented to the hair shafts.


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