Nasal histamine responses in nonallergic rhinitis with eosinophilic syndrome.

NARES, nonallergic rhinitis with eosinophilic syndrome, is a special form of chronic and persistent inflammatory rhinitis, which occurs in patients who are nonatopic. It is characterized by sneezing attacks, profuse aqueous rhinorrhea, nose-palate pruritus, nasal obstruction, and, occasionally, loss of the sense of smell.1 Its acute stages are triggered by various factors, including, for instance, temperature changes, intense perfume, and particular climatic conditions. Nasal cytology shows a predominance of eosinophils.2 Nonatopy is characterized by negative diagnostic allergy tests.3 Patients with NARES show more severe nasal symptoms compared with other types of allergic and nonallergic rhinitis, and they risk developing obstructive sleep apnea.4 Patients with chronic rhinitis show a 2–14% occurrence. Usually, it occurs as an isolated form, but it can be associated with bronchial hyperreactivity or as intrinsic asthma in 50% of patients, with no correlation between the increase in eosinophils count in induced sputum, and in nasal secretion5, with aspirin intolerance and nasal polyps. NARES may be an early sign of aspirin-exacerbated respiratory disease, characterized by asthma, nasal polyps, and nonsteroidal anti-inflammatory drug intolerance.6 Pathogenetic factors could include chronic, nonspecific release of histamine, and self-perpetuating eosinophilic infiltration, with nasal smear that shows more than 25% eosinophils as a diagnostic criterion.2 Nonspecific nasal hyperactivity (NSNH), which is the correlation between nasal responsiveness to nonspecific nasal provocation tests (NSNPT) and the response to everyday life stimuli, is typical of allergic and nonallergic rhinitis, and can entail vascular and glandular activation as well as the activation of different neuroregulating systems, which thus determines the type of response to nasal stimulation.7 In particular, in allergic rhinitis, NSNH requires a certain degree of inflammation, which is ensured by the eosinophil cationic protein and by eosinophils at a later stage of the allergic reaction.8 Hence, NSNH and the inflammation of the upper airways could be correlated with each other. This study aimed at determining whether NSNH is present in NARES and to what extent, whether eosinophilia diagnosed through nasal cytology is correlated with the respiratory and mucociliary clearance functions, and whether it is possible to grade NSNH based on the nasal reactivity classes.9