Wet Combing Best Way to Spot Head Lice
Study Shows Wet Combing Trumps Visual Inspection for Detecting Active Lice Infestation
WebMD News Archive
March 19, 2009 -- Combing through a child's wet hair rather than a simpler
visual inspection may be the best way to detect an active head lice
infestation, according to a new study.
Head lice infestation is one of the most common childhood infections,
affecting 1% to 3% of 6- to 12-year olds in industrialized countries. The tiny
head louse is a parasite that attaches to the scalp and is spread easily among
children in close contact, such as classrooms.
But until now, researchers say the accuracy of the two most common methods
used to detect head lice and their eggs or nits, wet combing and visual
inspection, has not been put to the test.
The results of the study suggest that the wet-comb method is much more
accurate at detecting active head lice infestation in children. But visual
inspection remains a useful tool for teachers, parents, and other caregivers to
measure epidemics of head lice and determine how many children are
"Usually, diagnosis of head lice infestation is made by the visual
inspection of the hair and scalp," write researcher Claudia Jahnke, MD, of
the City Health Department of Braunschweig, Germany, and colleagues in the
Archives of Dermatology. "The alternative is the use of a detection
comb, either directly on dry hair or after the hair has been moistened with
conditioner. In both cases the hair is systematically combed from the scalp to
The advantage of the visual inspection method is that it is easy and fast.
The wet-comb method, on the other hand, is more time consuming and requires
special equipment and instruction.
In the study, researchers compared the effectiveness of the two head lice
detection methods in 300 children attending German schools with head lice
epidemics in 2007.
The results of the study show the visual inspection method underestimated
the prevalence of active head lice infestation by a factor of 3.5.
Wet combing was much better at detecting active head lice infestations,
correctly identifying them in 90.5% of children, compared with a 28.6% accuracy
rate for visual inspections.
But visual inspections were better at detecting "historic" head lice
infestations -- that is, children who have nits in their hair but no lice.
Researchers say that in industrialized countries, most children only carry a
few head lice. Therefore, the optimal detection method should identify those
with even a single live louse who have the potential to spread the parasite,
which makes wet combing the preferred method to detect active infestations.