Circadian variation in nasal reactivity in children with allergic rhinitis: Correlation with the activity of eosinophils and basophilic cells

Background: In allergic rhinitis, the major symptoms of runny nose, sneezin g, and stuffy nose tend to become worse upon waking up in the morning, and yet the mechanisms underlying this phenomenon are poorly understood. We inv estigated whether the worsening of allergic rhinitis in the morning is asso ciated with changes in the activity of inflammatory cells. Methods: Nasal r eactivity to methacholine was assessed twice in 8 children with allergic rh initis and 8 healthy control subjects at 6.00 a.m. and 3.00 p.m. The amount s of eosinophil cationic protein (ECP), histamine and tryptase in induced n asal secretions and peripheral blood were also measured. Results: Nasal rea ctivity to methacholine was higher at 6.00 a.m. not only in patients but al so in healthy controls. Serum ECP and plasma histamine levels showed no cir cadian patterns. On the other hand, significantly higher levels of inflamma tory activation products were found in nasal secretions at 6.00 a.m., thus showing a direct association with nasal reactivity. Conclusion: These resul ts suggest that the circadian variation in nasal reactivity is associated w ith changes in the activity of eosinophils and basophilic cells in the nasa l mucosa.