IGF1 and acne: Early in acne inflammation, neutrophil recruitment activates macrophages, which regulate the migration and adhesion of inflammatory cells by releasing inflammatory factors such as IL-1α, IL-1β, IL-6 and TNF-α [27], and cytokines such as insulin-like growth factor-1 (IGF), TGF-β and platelet-derived growth factor (PDGF), which promote the differentiation of fibroblasts to myofibroblasts and the synthesis and secretion of extracellular matrix, which in turn leads to PS formation [28].