Wet-combing a child's hair may be the best way to determine if he or she has an active case of head lice, German researchers report.

Dr. Claudia Jahnke of the City Health Department in Braunschweig and her colleagues found that this method identified active infestations 91 percent of the time, while visual inspection of a child's hair only spotted 29 percent of the active infections.

To date, Jahnke and her team note in the Archives of Dermatology, the accuracy of wet combing and visual inspection, the two standard methods for identifying head lice, has not been evaluated "appropriately." To investigate, the researchers studied 304 children 6 to 12 years old from five different schools where head lice infestation was an ongoing problem.

Each child first underwent a visual inspection of the hair and scalp at the temples, behind the ears, and the neck, with the investigator using an applicator stick to part the hair. Then a different investigator combed through the child's hair with a lice comb after dampening the hair with a conditioner. The investigator performing the second examination was not told whether the first had identified signs of infestation.

The researchers found lice eggs or nits in 79, or 26 percent, of the children, while 21, or 7 percent, of the children had live lice indicating active infestation.

Visual examinations detected 86 percent of the cases of children with eggs or nits only, compared to 68 percent for wet combing. Conversely, wet combing was much more likely to identify the presence of live lice than visual examination; the researchers state that the visual method used alone would have underestimated the presence of active infestation 3.5 fold.

The issue of whether eggs alone indicate active lice infestation is controversial, the researchers note; in some European countries, lice-killing medication will not be used on children who have eggs in their hair but do not have live lice.

Based on the findings, the researchers conclude, while visual inspection is the best way to identify the prevalence of past infections in a group of children, wet combing is much more accurate for identifying active infestations.