Editorial on the Research Topic Physiology and pathophysiology of the olfactory system One of the intriguing features of the mammalian olfactory system is the integration of newly generated sensory neurons and interneurons in the olfactory bulb throughout our life. The continuous reconstitution of the olfactory neural circuit that arises from the integration could modify the olfactory information processing, and thus impair the olfactory image of objects. ...to maintain the olfactory perception, the olfactory system has developed homeostatic plasticity which works under physiological and even pathophysiological conditions. Intranasal administration of eosinophilic cationic protein damaged the olfactory neuroepithelium by inducing apoptosis, but this damage was largely prevented by insulin administration. ...insulin administration might lead to the development of new therapeutic agents for olfactory neuroepithelial injury.