Non-allergic rhinitis (NAR) is a common disorder, which can be defined as 
chronic nasal inflammation, independent of systemic IgE-mediated mechanisms. 
Symptoms of NAR patients mimic those of allergic rhinitis (AR) patients. 
However, AR patients can easily be diagnosed with skin prick test or 
allergen-specific IgE measurements in the serum, whereas NAR patients form a 
heterogeneous group and are difficult to diagnose because of an extensive list 
of different phenotypes, all varying in severity, underlying etiology and type 
of inflammation. Characterization of those phenotypes, mechanisms and management 
of NAR represents one of the major unmet needs in the field of allergic and 
non-allergic diseases. This review aims at providing a comprehensive overview of 
the state of the art in classifying the NAR patients and focuses on the 
neuro-immune mechanisms involved in allergic and non-allergic rhinitis, 
including reflections on the pathophysiology and the currently available 
treatment options.