As interfaces progress beyond wearables and into intrinsic human augmentation, the human body has become an increasingly important topic in the field of HCI. Wearables already act as a new layer of functionality located on the body that leads us to rethink the convergence between technology and fashion, not just in terms of the ability to wear, but also in how devices interact with us. Already, several options for wearable technology have emerged in the form of clothing and accessories. However, by applying sensors and other computing devices directly onto the body surface, wearables could also be designed as skin interfaces. In this paper, we review the wearability factors impacting wearables as clothes and accessories in order to discuss them in the context of skin interfaces. We classify these wearability factors in terms of body aspects (location, body movements and body characteristics) and device aspects (weight, attachment methods, accessibility, interaction, aesthetics, conductors, insulation, device care, connection, communication, battery life). We discuss these factors in the context of two different example skin interfaces: A rigid board embedded into special effects makeup and skin-mounted soft materials connected to devices.