This pleiotropic nature of IL-33 (Figure 2) is likely to 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, chronic obstructive pulmonary disease (COPD), fibrotic diseases, musculoskeletal diseases, inflammatory bowel diseases, diseases of the central nervous system (Alzheimer), graft vs. host disease (GVHD), obesity, diabetes, and cancer (3). Here, IL33 is linked to allergic disease.