Dermal Toxicity of a Repellent Formulation Containing Piper Aduncum Linnaeus (Piperales: Piperaceae) Essential Oil

It has been shown in previous research that Piper aduncum Linnaeus essential oil has the potential to be developed as an alternative mosquito repellent. When the essential oil was formulated into cream, it was able to provide >2h of protection against Aedes aegypti in the laboratory; thus, it can be commercialized as an alternative to synthetic repellent especially N, N-diethyl-3-methylbenzamide (DEET). In this study, the irritation and sensitization potential of a cream formulation containing P. aduncum essential oil was investigated to verify its safety for application purposes. The P. aduncum essential oil was formulated into a cream containing 10% of the essential oil for irritation and skin sensitization assays on New Zealand white rabbits and guinea pigs (Hartley strain), respectively, following the ISO10993-10:2010 (E) guidelines. The macroscopic and histological observations from both assays revealed that the cream formulation containing P. aduncum essential oil caused slight irritation on rabbit skin, with a Primary Irritation Index (PII) of 1.54; however, no positive response was detected in the skin sensitization assay. In conclusion, the cream formulation containing 10% P. aduncum essential oil was slightly irritating to rabbit skin but did not cause sensitization in the animals tested.