This study was designed to analyse prostaglandins (PGs) in human nasal lavage fluid using the combination of microcolumn high performance liquid chromatography and a He/Cd laser induced fluorescence detection system. Forty-seven patients with allergic rhinitis and 12 healthy volunteers were investigated. Four species of PG, i.e. PGD2, PGE2, PGF2 alpha, and 6-keto-PGF1 alpha were detected in the nasal lavage fluid. Concentrations of PGD2 (1.33 +/- 0.17 nmol/ml) and PGE2 (0.87 +/- 0.11 nmol/ml) in nasal lavage fluid from patients with allergic rhinitis (the allergy group) were significantly increased compared with those of volunteers (the control group, 0.23 +/- 0.16 nmol/ml, 0.29 +/- 0.19 nmol/ml, respectively). On the other hand, no significant differences were observed in concentrations of either PGF2 alpha or 6-keto-PGF1 alpha between the control group and the allergy group. Histamine concentration in nasal lavage fluid was significantly increased in the allergy group (53 +/- 7.6 nmol/l) compared with the control group (3.4 +/- 1.0 nmol/l). No significant correlation was observed between PGD2 and histamine concentration (r = 0.24), or between PGE2 and histamine concentration (r = 0.08) in nasal lavage fluid from patients with allergic rhinitis. Treatment with oxatomide, an anti-histamine and anti-allergic drug, significantly improved symptom scores, but did not alleviate them completely. Concentrations of each PG detected in nasal lavage fluid did not change significantly after oxatomide treatment. It is concluded that, not only histamine but also PGs, particularly PGD2 and PGE2, might be involved in the genesis of allergic rhinitis.