In addition, the peritoneal fluid of EM patients with CPP is characterized by an elevated level of PGE2, tumour necrosis factor-α (TNF-α), nerve growth factor (NGF), and CCL5 (C-C chemokine ligand 5:), as well as interleukin (IL) IL-8 and IL-1β [63,64,65]. Here, NGF is linked to erythema multiforme.