Objectives: Antioxidant nutrients like carotenoids, tocopherols and vitamin C have been suggested to protect against allergic rhinitis and allergic sensitisation but scientific evidence is scarce. The aims of the study were to measure the plasma concentration of six carotenoids, alpha- and gamma-tocopherol and vitamin C as biomarkers of the intake, absorption and subsequent metabolism of these nutrients, and to assess their association with allergic rhinitis and sensitisation.

Method: Data from a cross-sectional study on representative dietary and lifestyle habits of the population of Bavaria, Germany, were analysed. The plasma levels of six carotenoids (alpha-carotene, beta-carotene, lycopene, lutein/zeaxanthin, canthaxanthin and cryptoxanthin) as well as of alpha-tocopherol, gamma-tocopherol and vitamin C were measured in 547 adults aged between 19 and 81 years. Participants with specific serum immunoglobulin E > or =700 U l(-1) were categorised as sensitised. The association of plasma antioxidant levels, allergic rhinitis and allergic sensitisation was assessed by means of unconditional logistic regression models.

Results: We observed a negative association between plasma total carotenoids and the prevalence of allergic rhinitis, with odds ratio (95% confidence interval) of 1.13 (0.54-2.39) for the second, 0.72 (0.33-1.58) for the third and 0.44 (0.19-1.03) for the fourth quartile of total carotenoids concentration (P for trend=0.0332); results for lycopene failed to reach statistical significance (P=0.0608). Other single carotenoids, tocopherols and vitamin C were unrelated to allergic rhinitis. Allergic sensitisation was negatively associated with plasma gamma-tocopherol, with odds ratio (95% confidence interval) of 0.92 (0.51-1.65) for the second, 1.00 (0.56-1.80) for the third and 0.45 (0.23-0.88) for the fourth quartile of plasma gamma-tocopherol concentration (P for trend=0.0410). No other antioxidant was significantly related to allergic sensitisation.

Conclusions: High plasma carotenoid concentrations reflecting a diet high in various fruits and vegetables might have a protective effect on allergic rhinitis in adulthood.