The HPLC-MS and HPLC-MSn analysis techniques used in this study according to recent FDA recommendations  confirm the existence of verruculogen and other mycotoxins associated with conidia. The identification of the toxins secreted by A. fumigatus and their role in humans is a long-running enterprise involving microbiology, chemistry, and mammalian cell cultures. For the first time, we are including verruculogen as a toxin with deleterious effects on respiratory epithelial cells. Whatever the exact role of verruculogen, it is not the only factor involved in the prevalence of A. fumigatus in invasive disease compared with other moulds. Verruculogen is, for instance, secreted by Penicillium verruculosum, which has never been implicated in invasive disease. Verruculogen may act first, leading to settlement of the fungus and subsequently allowing other toxins to be produced if the fungus grows. Additionally, verruculogen might be synergistic or antagonistic with other molecules or proteases produced by A. fumigatus.