Variation in cutaneous perfusion due to synthetic pyrethroid exposure

Synthetic pyrethroids are neurotoxic insecticides with a low mammalian toxicity. Prior investigations have found these agents to be neither cutaneous irritants nor sensitisers. Clinically demonstrable inflammation, as judged by erythema, oedema, or vesiculation, has not been apparent. Nevertheless, paraesthesia does result from cutaneous exposure. In this investigation technical grade flucythrinate was applied to the forearms of human participants twice daily for five consecutive days. Laser Doppler velocimeter measurements were made before each topical application, with histamine phosphate being intradermally injected on termination of the study. Results of both laser Doppler velocimetry and histamine induced axon reflex vasodilatation were not statistically significant at an alpha = 0.05 level. This investigation suggests that the synthetic pyrethroids have little influence on neurogenic vasodilatation on topical exposure.