<p>Trichloroethylene (TCE) remains a versatile organic solvent used globally. In recent years, immunological occupational diseases such as hypersensitivity syndrome (HS) and systemic sclerosis (SSc) have attracted attention in terms of the number of patients and the life-threatening consequences. This review summarizes mechanisms underlying HS pathogenesis based on the available literature. TCE-HS is a disease attributable to anti-CYP2E1 autoantibodies and HLA-B13:01 as susceptibility gene and is characterized by systemic skin lesions, severe-to-moderate liver damage, fever above 38&#xa0;°C, leukocytosis, lymphadenopathy, and human herpesvirus 6 (HHV6) reactivation with elevated inflammatory cytokines, which are all similar to the characteristics of drug-induced HS. TCE-HS occurs on average 1&#xa0;month after the commencement of exposure to TCE, which is shorter than the corresponding period for SSc. Recent epidemiological and animal studies have clarified the mechanism of pathogenesis: the oxidative metabolites chloral hydrate, dichloroacetyl chloride, and trichloroethanol, which are produced by CYP2E1, amplify the methylation of CD4⁺ T cells and activate them, resulting in the upregulation of cytokines such as TNF-α. Subsequently, some unidentified but oxidized metabolite haptens are assumed to activate CD8⁺ T cells with HLA-B*13:01, resulting in the production of anti-CYP2E1 autoantibodies. Subsequently, HHV6 is reactivated, leading to the development of skin and hepatic injuries. Whether skin lesions develop through a pathophysiological mechanism originating from hepatic lesions or by the same mechanism as the development of hepatic lesions remains unclear. Although disease contours have been clarified, further studies are required to elucidate its pathogenesis.</p>