Pathogenic Mechanisms of Idiopathic Nonallergic Rhinitis

Idiopathic nonallergic rhinitis (iNAR) has been difficult to define because of the long differential diagnosis of rhinopathy in the absence of allergic rhinitis. iNAR has traditionally been a diagnosis of exclusion with no clear unifying pathophysiology. Increased sensitivity to triggers such has climate changes, cold air, tobacco smoke, strong odors, and perfumes have been thought to be characteristic, but recent studies do not support this hypersensitivity hypothesis. New investigations of the local nasal environment and systemic "functional" syndromes have offered new insights into this condition. iNAR may be a heterogenous disorder that includes (1) anatomic abnormalities requiring nasal endoscopy for diagnosis, (2) incipient, local atopy (entopy), (3) dysfunction of nociceptive nerve sensor and ion channel proteins, and (4) autonomic dysfunction as found in chronic fatigue syndrome and other functional disorders.