This pleiotropic nature of IL‐33 explain why IL‐33 has been implicated in a wide variety of non‐allergic diseases, including infectious diseases (fungal, helminth, protozoa, bacterial and viral infection), cardiovascular diseases, COPD, fibrotic diseases, musculoskeletal diseases, inflammatory bowel diseases, diseases of the central nervous system (Alzheimer), graft versus host disease (GVHD), obesity, diabetes and cancer. The gene discussed is IL33; the disease is graft versus host disease.