Arena tests with piperonal, a new louse repellent.

Piperonal, once used to kill lice in Australian hospitals, was acclaimed as an effective pediculicide (Corlette, 1925) by the standards of the day. It is unusual in also exhibiting a repellent action against lice, a property only recently realised. A new, easy to use, low-fragrance, pump action spray, which incorporates 2% piperonal, was tested in the laboratory using clothing lice in an arena test and was found to exhibit consistently high repellency after half an hour, dropping only slightly after 24 hours. A well known multi-purpose insect repellent, diethyltoluamide (DEET), was then tested against piperonal. A 2% solution of piperonal was found to be almost twice as effective as a 50% solution of DEET. In arena tests using lice with the tip segments of both antennae removed, no behavioural differences or statistically significant differences from a random distribution could be found between untreated and Rappell-treated areas. This strongly suggests that sense organ(s) on the tip of the antenna are necessary for detection of the repellent. Although there can be no strict correlation between results in the laboratory and potential efficacy in the field, materials such as insecticides found to be effective in the laboratory have been found to be equally effective in the field. Furthermore, what with the threat of resistance to head lice insecticides, ineffectual treatment and the lack of contact tracing, a repellent would be of obvious use in the control of head lice.