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, sneezing, and stuffy nose tend to become worse upon waking up in the morning, and yet the mechanisms underlying this phenomenon are poorly understood. We investigated whether the worsening of allergic rhinitis in the morning is associated with changes in the activity of inflammatory cells. Methods: Nasal reactivity to methacholine was assessed twice in 8 children with allergic rhinitis and 8 healthy control subjects at 6.00 a.m. and 3.00 p.m. The amounts of eosinophil cationic protein (ECP), histamine and tryptase in induced nasal secretions and peripheral blood were also measured. Results: Nasal reactivity to methacholine was higher at 6.00 a.m. not only in patients but also in healthy controls. Serum ECP and plasma histamine levels showed no circadian patterns. On the other hand, significantly higher levels of inflammatory activation products were found in nasal secretions at 6.00 a.m., thus showing a direct association with nasal reactivity. Conclusion: These results suggest that the circadian variation in nasal reactivity is associated with changes in the activity of eosinophils and basophilic cells in the nasal mucosa.