Abstract
Respiratory Sensitisation is a serious health condition that can have life-threatening consequences and that is regulated under the UN globally harmonised system (GHS) and the European system for classification, labelling and packaging of hazardous chemicals and mixtures (CLP). In the absence of widely accepted and validated approaches for the prospective identification of chemicals that induce respiratory sensitisation, classification relies on clinical evidence of causation of substance-specific respiratory hypersensitivity, typically seen as occupational asthma. Significant advances have been made in recent years in the phenotyping of both asthma and occupational asthma since the introduction of criteria and guidance for classification that are not reflected in the current criteria and guidance. Typically generated clinical data, including specific inhalation challenge tests, while sufficient for diagnosis and health management are often deficient for regulatory classification purposes as they are often not sufficiently documented to meet the required standards and fail to reliably distinguish between occupational asthma and non-specific irritant exacerbation of pre-existing asthma that is regulated under another classification endpoint. A multistakeholder forum is proposed to facilitate revision of the now outdated criteria and guidance. Differences between underlying mechanisms of respiratory sensitisation and occupational asthma jeopardise establishment of an Adverse Outcome Pathway for respiratory sensitisation and development of alternative methods, including non-animal methods.