Late phase responses after nasal challenges with allergen and histamine in asthmatic children with perennial nasal allergy.

Objective: Late phase response (LPR) is difficult to investigate in patients with perennial nasal allergy because of their continuous presentation with nasal symptoms. Contribution of histamine to the LPR is also controversial. In this study, we investigated whether exogenous histamine can induce LPR in asthmatic patients with perennial nasal allergy to house dust. Methods: A total of 40 asthmatic children were divided into clinical, subclinical and non-rhinitis groups based on their daily nasal symptoms. Changes in nasal patency and in inflammatory cells in nasal secretion were quantitatively measured for 6 h by acoustic rhinometry and light microscopy respectively before and after nasal challenge with allergen or histamine. Results: The allergen challenge produced a significant biphasic decrease in nasal patency in the subclinical group and a marginal decrease in the clinical group, with increases in eosinophils 6 h after the challenge. By contrast, histamine challenge induced significant responses in the clinical group and only a slight response in the subclinical group. Eosinophils also accumulated in nasal secretion of the clinical group to significant levels 6 h after histamine challenge. Eosinophil accumulation following histamine challenge was earlier than that after exposure to allergen. Conclusion: We conclude that LPR can be demonstrated in asthmatic children with perennial nasal allergy. Exposure to exogenous histamine also induced LPR, mediated mainly by eosinophil-related mediators.