Identification of Allergens in Complex Mixtures and Products

Abstract

Identifying contact allergens among the myriad of chemicals used in commercial products is an extremely arduous task. This is even more difficult in the case of components of complex mixtures such as natural extracts and essential oils. Today, non-animal alternative methods validated to assess the sensitizing potential of chemicals are, overall, unable to completely predict the skin sensitization potential of these complex mixtures of chemicals. Moreover, toxicological profiles are very difficult to extrapolate from the mere sum of the profiles of the individual constituents as required today. In this context, hazard identification remains still one of the best solutions for risk assessment. This chapter presents a brief overview of methods allowing the identification of allergens in complicated chemical mixtures, going from bioassay-guided fractionation and combination with structure-activity relationships studies to more recent new techniques developed to trap and identify reactive intermediates in natural extracts during air oxidation. Practical applications are exposed such as the case of oak moss absolute. Also, the assessment of the sensitization potential of tea tree oil is a typical example of the challenges that toxicologists encounter in the safety evaluation of essential oils. Methods based on chemical reactivity and fluorescence trapping, basically studying the oil after aging and air oxidation, are discussed. Hence, a great deal of progress has been accomplished during the last years for the identification of chemicals culprit of the sensitizing potential of very complex chemical mixtures. That being said, the identification of allergens in complex mixtures and products is still a challenging puzzle.