Patch design
A 3D-printed allergen-delivery device, comprising a 3x5x1 cm open-sided chamber31 (1.5 mL volume) was custom-made for this study (figure 1), using Blocks One MKII printer (Blocks, Amadora, Portugal). The 3D prototype design used a cloud-based 3D modelling, computer-aided design and manufacturing software platform, FUSION 360 (Autodesk, Inc., California, U.S.A.). The device’s shape and size were tailored to cover a large body surface area, as this proved to increase allergen capture by skin dendritic cells and their migration to lymph nodes39. It was also necessary to ensure the feasibility of patch application with respect to the dog’s body size and shape and owners’ constraints regarding the dog’s aesthetics. A 1.75mm polylactic acid filament was used, as it is a biodegradable, eco-friendly, affordable material with favourable biocompatibility and safe degradation products.