Finally, as the physiological variations of olfactory performance can be attributed, at least partially, to the rs2590498 (A/G) polymorphism of the gene encoding for human odorant binding protein (hOBPIIa) [24,60,61], we investigated the role of this polymorphism in the olfactory function of IBD patients and HC subjects, also according to their BMI. The gene discussed is OBP2A; the disease is inflammatory bowel disease.