**2. Rhino-Cytology**

Nasal cytology is a very useful diagnostic method in rhino-allergology—it allows for the detection of cellular variations of an epithelium exposed to acute/chronic irritations or inflammations of different nature and makes it possible to diagnose some nasal pathologies [35,36]. The strengths of this methodology lie in the simplicity of the diagnostic examination; in fact, it is totally painless, safe, and fast, as it can be conducted in an outpatient clinic. Starting from the assumption that the nasal mucosa of the healthy individual consists normally of only four cytotypes, cytological diagnostics is based on a fundamental axiom that states that, if other cells, such as eosinophils, mastcells, bacteria, spores, and fungal hyphae, are present in the rhinocytogram, then the individual can be affected by a nasal pathology. A quantitative analysis of the pathological cells contained in the nasal mucosa and their state of rest or activation allows for the indication of a targeted therapy to the patient [37].
