TSLP and allergic disease: Typically, AAD is defined as an allergic response in individuals characterised by increased serum IgE, airway inflammation, airway remodelling (including peribronchial fibrosis and increased collagen deposition), increased type 2 cytokine profile (e.g. Interleukin (IL) 4, IL5, IL13, IL25, IL33, thymic stromal lymphopoietin (TSLP)), airway eosinophilia, mucus hypersecretion, and airway hyperresponsiveness (AHR).1, 13, 18