Bullous pemphigoid (BP) is the most common autoimmune blistering skin disease (Schmidt and Zillikens, 2013). BP has become more common over the past two decades (Försti et al., 2014; Joly et al., 2012; Langan et al., 2008). However, the underlying causes of the increasing incidence of BP are poorly understood. Altogether, over 50 drugs have been reported to induce BP (Stavropoulos et al., 2014). The use of dipeptidyl peptidase-4 inhibitors (DPP-4i), a class of drug used for the treatment of diabetes, has recently been scrutinized as a risk factor for BP, both in case reports (see Supplementary Table S1 online) and in national pharmacovigilance database reports (Bene et al., 2016; García et al., 2016), but large population-based studies are lacking.