We evaluate the efficacy of products such as shampoos at controlling lice according to published scientific methods. Our test organism is the clothes louse Pediculus humanus humanus, which is almost identical to the head louse in terms of morphology and biology. Leading experts in the field even consider them to be the same species. Fig. 1 shows an adult clothes louse, and a short video sequence shows the lice in motion.
We can investigate both the efficacy of products against adult lice and against louse eggs. Concerning the latter, we always test two age classes, as different developmental phases of the eggs (see figs. 2 and 3) may display differing susceptibility to the products tested.
Fig.2: One day-old louse egg attached to a hair.
Fig.3: Five days-old louse egg showing a distinct red eyespot.
Fig. 4: Incubation of lice in a water bath.
Our standard test protocol closely mimics the conditions under which the test products are to be used: we incubate the lice or their eggs in the test solution at 35 °C for a fixed period (see fig. 4), wash them according to a defined procedure, then evaluate their vitality over a period of several days.
As the eggs of the lice we test are normally attached to human hair we also can evaluate whether test products are able to detach the eggs from hair.
Video: Adult clothes lice on a piece of dress material.