Bergamot oil intended for topical use - attempts for a risk assessment of phototoxicity

Bergamot oil is a widely used aromatic ingredient, e.g. in food and cosmetics. Its use is often limited due to reported phototoxicity, usually attributed to bergapten content.The aim of this study was to clarify the differences in the phototoxicity of several bergamot oils obtained from different suppliers. The phototoxicity of the samples was evaluated in vitro in the 3T3 NRU Phototoxicity Test (PT) and a phototoxicity test on reconstructed human skin model (EpiDermTM, Mattek). In addition, in case of non-phototoxic classification in the EpiDerm phototoxicity assay, photo-patch testing in a limited group of human volunteers was performed.Amongst 4 different samples, two phototoxic and two non-phototoxic oils were classified by 3T3 NRU PT, however, only on the basis of borderline phototoxicity results. Surprisingly, even samples classified borderline proved to be clearly phototoxic in the EpiDerm test. In general, the skin model test and human patch test provided concordant results. In both cases, it was estimated that bergamot oils (classified as non-phototoxic by 3T3 NRU PT) were safe for use up to 1 %. The skin model test therefore seems to be a useful tool in the risk assessment, since it enables to set a margin of safety before any testing in humans.Analytical analysis (applying capillary GC/MS) enabled identification and quantification of photoactive compounds present in the test samples. Besides bergapten, differences in citropten, bergamottin, geranial and neral content were identified. We conclude, that the different phototoxic effect depends also on the amount of these components.