that are excreted to the skin surface and form sebum. The function of sebum is still a matter of investigation. It is only hypothesized that sebum may play a role in the protection of skin from dehydration, ultraviolet radiation (UVR), wrinkling, and infection ( 1, 2 ). The sebaceous lipid mixture is highly complex and consists of triacylglycerols (TAG), diacylglycerols (DAG), and free fatty acids (FFA), which together account for 50-60% of its composition. Sebum also contains 20-30% wax esters (WE), 10-16% squalene (SQ), and 2-4% cholesterol esters (CE) ( 1, 2 ). Initial analyses of the components of the sebaceous lipid mixture conducted by led to the identifi cation of several different types of acyl chains in esters with glycerol, cholesterol, and waxes. Fatty acids (FA) with an odd number of carbon atoms, branched side chains, and sites of unsaturation at unconventional positions were characterized. However, information on the intact lipids remained to be determined. A detailed characterization of the lipid repertoire in sebum in physiologic and diseased conditions is very limited due to the unavailability of methods for the comprehensive and simultaneous analysis of whole lipids. Prior investigations of the composition of sebum have been mostly concerned with acne, a multifactorial skin disorder that affects the pilosebaceous unit. Currently, only a few parameters are addressed when investigating alterations in sebum, such as SQ levels and the composition of FA obtained from the hydrolysis of TAG, DAG, WE, and CE. The methodology for the targeted analysis of SQ involves gas chromatography (GC) with Abstract Sebum is a complex lipid mixture that is synthesized in sebaceous glands and excreted on the skin surface. The purpose of this study was the comprehensive detection of the intact lipids that compose sebum. These lipids exist as a broad range of chemical structures and concentrations. Sebum was collected with SebuTape TM from the foreheads of healthy donors, and then separated by HPLC on a C8 stationary phase with sub 2 µm particle size. This HPLC method provided high resolution and excellent reproduc- Skin is a metabolically active tissue that contains sebaceous glands, which are specialized organelles equipped for the synthesis of a broad spectrum of lipid compounds

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Bullous pemphigoid (BP) is the most frequent autoimmune subepidermal blistering disease provoked by autoantibodies directed against two hemidesmosomal proteins: BP180 and BP230. Its pathogenesis depends on the interaction between predisposing factors, such as human leukocyte antigen (HLA) genes, comorbidities, aging, and trigger factors. Several trigger factors, such as drugs, thermal or electrical burns, surgical procedures, trauma, ultraviolet irradiation, radiotherapy, chemical preparations, transplants, and infections may induce or exacerbate BP disease. Identification of predisposing and trigger factors can increase the understanding of BP pathogenesis. Furthermore, an accurate anamnesis focused on the recognition of a possible trigger factor can improve prognosis by promptly removing it.