Changes in nasal mucosal blood flux and air-flow resistance on unilateral histamine challenge

To investigate reflex vascular control in the nose, we challenged each side of the nose with 0.9% saline and histamine (0.3 mg aqueous) and observed changes in unilateral nasal airway resistance (Rnaw) and laser doppler flux (LDF) in response to contra-lateral and ipsilateral challenge in eight normal subjects. Preliminary studies demonstrated that the preferred site for observation of LDF was the nasal septum (same-day concordance 0.920; inferior turbinate 0.307). Ipsilateral contra-lateral saline induced no significant change to either parameter. Ipsilateral histamine produced a highly significant rise in LDF (757 arbitrary units SEM 94 at 3 min; baseline 489 SEM 75: P < 0.05) and Rnaw (baseline: 3.10, SEM 0.52; 5 min: 8.81, SEM 2.09 cmH2O/l/s: P < 0.01). Contra-lateral histamine produced a significant P < 0.05) fall in both (LDF 317, SEM 24 at 3 min; Rnaw 2.67, SEM 0.78 cm H2O/l/s at 6 min). This previously unrecorded observation suggests a neural reflex that increases the patency of the contra-lateral nostril after unilateral obstruction is provoked.